Understanding ASTM D2000 Classification System

ASTM D2000 is a widely recognized standard issued by the American Society for Testing and Materials (ASTM). This standard, primarily developed by the Society of Automotive Engineers (SAE), provides a comprehensive classification system for rubber products used in automotive applications. Its principal purpose is to simplify the specification and description of elastomer materials.

Our guide is designed to assist you in understanding and applying the ASTM D2000 standard to O-Rings and seals. We will delve into each ASTM D2000 line call-out segment, clearly explaining the meaning and importance of specification revision, measurement units, grade number, type and class, hardness, tensile strength, and additional requirement suffixes. With this guide, our goal is to demystify the complex terminology and codification of the ASTM D2000 standard. We aim to provide you with the knowledge to read and interpret these specifications, making selecting the right material for your specific needs easier.

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Decoding an ASTM D2000 Line Call-Out

Each line call-out comprises different segments, each representing certain specifications of the material. To guide this understanding, we will use the example below:








This line call-out contains 7 different segments that this guide will walk through:

  1. The Specification Revision
  2. Measurement Units Identification
  3. Grade Number
  4. Type and Class
  5. Hardness or Durometer
  6. Tensile Strength
  7. Additional Requirement Suffixes

1. Specification Revision






The first part of the line call-out is the specification revision. This refers to the revision year of D2000 to which the line call-out makes reference. For this example, ASTM-D2000-99 is the specification revision. The “-99” at the end of the standard number indicates the year (1999) when this specific version of the standard was either issued or reaffirmed.

2. Measurement Units






The next part of the ASTM line call-out indicates the units that will be used. If an M is present in the line call-out, it indicates that metric units will be used to measure tensile strength, temperature, and tear strength (MPa, °C, and kN/m, respectively). If no M is present, English units will be used (psi, °F, and ppi, respectively). For our example, the measurements will show in metric units.

3. Grade Number






The grade is indicated after the unit of measure specification (or the specification revision if the units of measure are English units). This denotes the level of test requirements to which a material may be subjected. Grade 1 shows that only basic properties are required, while Grades 2-9 need additional testing criteria, such as low-temperature brittleness or special heat aging tests. The material must meet some or all Grade 2 requirements in our example. Note that Grade Numbers may not be relevant to all material Types and Classes.

4. Type and Class






The Type and Class is a crucial part of an ASTM D2000 call-out.  A Type is denoted by a single letter following the Grade number. The Type represents the elastomer’s tensile strength capabilities after heat aging at a fixed time and given temperature. The single letter following the Type is referred to as the Class. The Class represents the elastomer’s resistance to swelling after submerging in ASTM Oil for a fixed time and given temperature. Together the Type and Class will indicate the polymer. In our example, the Type and Class are “HK”, which points to fluorinated elastomers such as Viton® or Fluorel.

Please refer to the table below for the most common polymers used for each type:


Classification System D2000

SAE J200 Material Designation (Type and Class)

Test of Polymer Most Often Used
AA Natural rubber, reclaimed rubber, SBR, butyl, EP polybutadiene, polyisoprene
AK Polysulfides
BA Ethylene propylene, high temperature SBR, butyl compounds
BC Chloroprene polymers (neoprene), cm
BE Chloroprene polymers (neoprene), cm
BF NBR polymers
BG NBR polymers, urethanes
CA Ethylene propylene
CE Chlorosulfinated polyethylene (Hypalon), cm
CH NBR polymers, epichlorohydrin polymer
DA Ethylene propylene polymers
DF Polyacrylic (butyl-acrylate type)
DH Polyacrylic polymers, HNBR
FC Silicone (high strength)
FE Silicones
FK Fluorinated silicones
GE Silicones
HK Fluorinated elastomers (Viton®, Fluorel, etc.)
KK Perfluoroelastomers


5. Hardness (Durometer)






Hardness or Durometer measures a material’s resistance to permanent indentation or deformation. It is often used as a proxy for the overall flexibility or rigidity of a material. It’s one of the key properties specified in ASTM D2000 line call-outs. Hardness is typically measured using the Shore A scale in the context of rubber or elastomeric products. The Shore A Durometer is the most common device to measure the hardness of elastomers, rubber, plastics, and non-metallic materials. For context, a rubber band may have a hardness around 25 Shore A, a car tire around 70, and a hard plastic skateboard wheel around 98 Shore A. The hardness of a material can impact its performance in applications, so understanding the durometer number in the ASTM D2000 specification can help in selecting the right material for your specific needs. For instance, a harder material might resist abrasion or deformation better but could also be less flexible.

In your ASTM D2000 line call-out, the hardness value is represented by the first digit after the Type and Class (“HK” for our example). Here the number is “7”, which refers to a hardness of 70 in Shore A units (±5). This means the material should have a hardness between 65 and 75 on the Shore A scale.

6. Tensile Strength






In an ASTM line call-out, the tensile strength immediately follows the durometer, and the unit of measurement (MPa or psi) is denoted by the presence of an “M” after the Specification Revision. If the measurements are in English units, the digits show psi, and only the first two digits of that measurement are indicated. In our example, the material’s tensile strength is 14 MPa. If this example were non-metric, the callout would be 20 (14 MPa = 2031 psi).

Tensile strength refers to the maximum amount of tensile (pulling) stress a material can withstand before falling or breaking. It is a crucial consideration for elastomers used in sealing applications, as it can significantly influence their performance under pressure and their durability. A higher tensile strength generally implies a stronger, more durable material, while a lower tensile strength could indicate a softer, more flexible material. However, it is essential to remember that tensile strength alone does not provide a complete picture of a material’s performance or suitability for a particular application. It’s just one among several properties, like hardness, elongation, and resistance to specific environments, that need to be considered when choosing a material for a specific application.

The first six characters of a line call-out give a lot of basic information about the type of elastomer required and its physical properties. Most specifications require more information to guarantee that the seal will meet the needs of the application.

7. Additional Requirement Suffixes






Suffixes are a combination of letters and numbers that indicate a material’s test and performance criteria. Each letter-number pair corresponds to a specific requirement. In our example, these requirement suffixes are A1-10, B38, C12, EF31, EO88, F15, and Z1. The suffixes indicate a heat resistance test, compression set test, resistance to ozone, fuel resistance, oil and lubricant resistance, low-temperature brittleness criteria, and a special criteria that must be specified in detail, respectively.

Below is a list of suffix call-out details. Refer to ASTM D2000 for expanded suffix call-out details.


Suffix Letter Test Required
A Heat Resistance
B Compression Set
C Ozone or Weather Resistance
D Compression-Deflection Resistance
EA Fluid Resistance (Aqueous)
EF Fluid Resistance (Fuels)
EO Fluid Resistance (Oils and Lubricants)
F Low-Temperature Resistance
G Tear Resistance
H Flex Resistance
J Abrasion Resistance
K Adhesion
M Flammability Resistance
N Impact Resistance
P Staining Resistance
R Resilience
Z Any Special Requirement (Specified in Detail)


In conclusion, understanding an ASTM D2000 line call-out helps decode critical information about a rubber material’s properties. It tells you about the specification revision, measurement units, grade number, type and class, hardness, tensile strength, and any additional requirements. Each segment provides a crucial detail about the material’s suitability for specific applications. While it may seem complex at first glance, this guide has hopefully simplified each component for you. Remember to fill out the form at the top of the page for a downloadable link to this guide, which you can reference anytime. We are here to assist you in making informed decisions about your material needs.