O-ring seals are circular rings of various cross-section configurations that are utilized in a slot or gland to seal off a passageway and prevent the escape or loss of a fluid, gas or pressure. An o-ring is characterized by three of its specific features: dimensions, material, and hardness of comprised material. Material and hardness specify the elastomer compound and durometer hardness of the compound that is used to manufacture the o-ring. An O-ring's dimensions are described by specifying its inside diameter(ID), outside diameter(OD) and its cross-section(CS). The design of an o-ring depends on some major and interrelated variables: the operating conditions or environment the seal will experience, the gland geometry into which the seal will be installed and the variables which accounts for so many different types of seals and applications.
You may have heard someone mention a number with a dash such as -012 or –213 when they refer to an o-ring. These dashed numbers are derived from the Aerospace Standard 'AS568B' that assigns a dashed number and tolerances to a specific size o-ring(ID X OD X CS). AS568B size o-rings, most referred to as standard size o-rings, are the most frequently used here in the USA. There are several other size standards throughout the world such as AS 568, BS1806, BS4518, ISO3601/01, DIN3771, SMS1588, NFT 47-501, JIS 2401, to mention a few.
Another specification of an o-ring description mentioned above, is the durometer hardness of the material that it is constructed of. Durometer is simply put: the measure of how far a durometer gauges indentor penetrates a rubber sample. You may see a description of 17/90 for instance. That is a number -017 o-ring with a 90 durometer material hardness. Rubber material can be made very soft(low durometer reading) to very hard(high durometer reading). The harder the material, the longer it will endure and the less prone it is to wear but still may not be suitably applicable for the parameters of its intended use. The hardness is usually called out in increments of 5 durometer points. As an example: 80, 85, 90 and so on. The hardness of rubber has a tolerance of ±5 points as well. This is due to the fact that the hardness is tough to control because of an array of variables involved in the compounding and the manufacturing process.
Below is a short list of available o-rings using the American AS568B standard format that would most commonly apply to paintball markers using such. Unless you purchase from a business that specializes in o-rings, chances are anyone assisting you at places such as ACE, Lowe's or Home Depot will have no idea what an AS568B number or durometer hardness standards are. Using the nominal inch dimensions will most likely be your best source of information to have with you when seeking replacements. You'll also find below a chart depicting the most common materials available. It describes the material name and a short description of the specific material and temperature parameters.
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AS568B
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Nominal Inches
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Actual Inches
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Actual Millimeters
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Number
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ID
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OD
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CS
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ID
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CS
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ID
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CS
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-001
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1/32
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3/32
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1/32
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.029±.004
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.040±.003
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0.74±0.10
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1.02±0.08
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-002
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3/64
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9/64
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3/64
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.042±.004
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.050±.003
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1.07±0.10
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1.27±0.08
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-003
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1/16
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3/16
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1/16
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.056±.004
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.060±.003
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1.42±0.10
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1.52±0.08
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-004
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5/64
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13/64
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1/16
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.070±.005
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.070±.003
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1.78±0.13
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1.78±0.08
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-005
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3/32
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7/32
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1/16
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.101±.005
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.070±.003
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2.57±0.13
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1.78±0.08
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-006
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1/8
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1/4
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1/16
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.114±.005
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.070±.003
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2.90±0.13
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1.78±0.08
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-007
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5/32
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9/32
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1/16
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.145±.005
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.070±.003
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3.68±0.13
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1.78±0.08
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-008
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3/16
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5/16
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1/16
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.176±.005
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.070±.003
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4.47±0.13
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1.78±0.08
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-009
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7/32
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11/32
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1/16
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.208±.005
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.070±.003
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5.28±0.13
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1.78±0.08
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-010
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1/4
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3/8
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1/16
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.239±.005
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.070±.003
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6.07±0.13
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1.78±0.08
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-011
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5/16
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7/16
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1/16
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.301±.005
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.070±.003
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7.65±0.13
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1.78±0.08
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-012
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3/8
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1/2
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1/16
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.364±.005
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.070±.003
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9.25±0.13
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1.78±0.08
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-013
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7/16
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9/16
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1/16
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.426±.005
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.070±.003
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10.82±0.13
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1.78±0.08
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-014
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1/2
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5/8
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1/16
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.489±.005
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.070±.003
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12.42±0.13
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1.78±0.08
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-015
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9/16
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11/16
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1/16
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.551±.007
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.070±.003
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14.00±0.18
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1.78±0.08
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-016
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5/8
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3/4
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1/16
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.614±.009
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.070±.003
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15.60±0.23
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1.78±0.08
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-017
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11/16
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13/16
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1/16
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.676±.009
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.070±.003
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17.17±0.23
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1.78±0.08
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-018
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3/4
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7/8
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1/16
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.739±.009
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.070±.003
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18.77±0.23
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1.78±0.08
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-019
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13/16
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15/16
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1/16
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.801±.009
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.070±.003
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20.35±0.23
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1.78±0.08
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-020
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7/8
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1
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1/16
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.864±.009
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.070±.003
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21.95±0.23
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1.78±0.08
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-021
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15/16
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1-1/16
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1/16
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.926±.009
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.070±.003
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23.52±0.23
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1.78±0.08
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-022
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1
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1-1/8
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1/16
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.989±.010
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.070±.003
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25.12±0.25
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1.78±0.08
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-023
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1-1/16
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1-3/16
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1/16
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1.051±.010
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.070±.003
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26.70±0.25
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1.78±0.08
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-024
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1-1/8
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1-1/4
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1/16
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1.114±.010
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.070±.003
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28.30±0.25
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1.78±0.08
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-025
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1-3/16
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1-5/16
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1/16
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1.176±.011
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.070±.003
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29.87±0.28
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1.78±0.08
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-026
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1-1/4
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1-3/8
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1/16
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1.239±.011
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.070±.003
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31.47±0.28
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1.78±0.08
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-027
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1-5/16
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1-7/16
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1/16
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1.301±.011
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.070±.003
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33.05±0.28
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1.78±0.08
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-028
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1-3/8
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1-1/2
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1/16
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1.364±.013
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.070±.003
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34.65±0.33
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1.78±0.08
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-029
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1-1/2
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1-5/8
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1/16
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1.489±.013
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.070±.003
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37.82±0.33
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1.78±0.08
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-030
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1-5/8
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1-3/4
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1/16
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1.614±.013
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.070±.003
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41.00±0.33
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1.78±0.08
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O-Ring Material Chart
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TEMPERATURE
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MATERIAL
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-55 to 125 C
-67 to 257 F
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Nitrile (Buna-N)
Most commonly used O-Ring material type. Resistant to many hydrocarbon fluids and petroleum oils, greases, and hydraulic fluids. Resistant to water, alcohols and many chemicals. Not suitable for ketones, esters, aldehydes and chlorinated or nitro-hydrocarbons.
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-115 to 250 C
-175 to 482 F
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Silicone
Suitable for use in air, high aniline point petroleum oils, ozone and many oxidizing chemicals. Not recommended for most solvents, low aniline point petroleum oils, or concentrated acids.
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-55 to 150 C
-67 to 302 F
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Neoprene
Resistant to many chemicals and acids as well as ozone. Moderate resistance to petroleum oils and good resistance to commonly used refrigeration fluids. Not resistant to strong oxidizing acids, ketones, esters or aromatic or chlorinated hydrocarbons.
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-149 to 232 C
-300 to 450 F
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Teflon (TFE)
For use where total solvent to chemical resistance, or extremely high or low temperature resistance, is desired in installations similar to those in which elastomeric materials are customarily used, with the exception of reciprocation motion. Typical applications: gaskets, jam seals, valve discs or seats, and lubricant or weather seals on slow rotary motion.
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-40 to 225 C
-40 to 437 F
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Viton
Resistant to aliphatic, aromatic and halogenated hydrocarbons as well as acids and animal and vegetable oils. Not recommended for ketones, low molecular weight esters or nitro-hydrocarbons.
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-55 to 150 C
-67 to 320 F
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Ethylene-Propylene (EPR-EPDM)
Resistant to animal and vegetable oils, ketones, ozone, and oxidizing chemicals. Not resistant to petroleum oils, fluids or fuels, or aromatic hydrocarbons.
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-55 to 100 C
-67 to 212 F
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Polyurethane (Urethane)
Resistant to ozone, fats, petroleum oils and fluids. Outstanding abrasion resistance. Not suitable for concentrated acids or ketones, esters or chlorinated hydrocarbons.
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Technical Information
