RMA Rubber Tolerance Chart
The Rubber Manufacturers Association tolerance tables define the standard dimensional and geometric grades — A1/A2, B1/B2, C1/C2 and beyond — for molded, extruded and lathe-cut rubber parts. Engineers use it to set realistic tolerances that match a part's function and cost target; ARC molds and extrudes to every RMA class, or tighter where your application demands it.
Request a Quote All Charts & Tools →Using the RMA tolerance chart to spec your rubber part
The RMA rubber tolerance chart is the industry reference engineers reach for when they need to assign realistic dimensional tolerances to a molded, extruded or lathe-cut part. Searching for the RMA standard molding tolerances, extrusion tolerance classes, or the A1/A2, B1/B2 and C1/C2 grades usually means you are pinning down a drawing callout — matching each dimension to the tightest class the part actually needs so it fits and functions without over-specifying and driving up cost. Reading the chart correctly keeps tolerances defensible on the print and quotable on the floor.
ARC molds and extrudes to every RMA class, and tighter where the application demands it. Choose from a full range of elastomers — EPDM, silicone, nitrile, Viton, neoprene and more — compounded to your service conditions and produced under our ISO 9001:2015 and IATF 16949:2016 quality systems. Send a drawing or target dimensions and our engineers confirm the achievable grade, tooling and lead time, typically with a quote in one business day.
Need Custom Rubber Parts to Specific RMA Tolerances?
American Rubber Corp manufactures custom molded rubber parts to RMA Class A1, A2, A3, and A4 tolerances, and extruded products to RMA Class E1, E2, E3, E4. We work with your ASME Y14.5 GD&T drawings. ISO 9001:2015 + IATF 16949 certified.
Metric Tolerances (mm)
| Nominal Dimension | A1 | A2 | A3 | A4 | |||||
|---|---|---|---|---|---|---|---|---|---|
| above | up to andincluding | Fixed | Closure | Fixed | Closure | Fixed | Closure | Fixed | Closure |
| 0 | 10 | 0.1 | 0.13 | 0.16 | 0.2 | 0.2 | 0.32 | 0.32 | 0.8 |
| 10 | 16 | 0.13 | 0.16 | 0.2 | 0.25 | 0.25 | 0.4 | 0.4 | 0.9 |
| 16 | 25 | 0.16 | 0.2 | 0.2 | 0.32 | 0.32 | 0.5 | 0.5 | 1 |
| 25 | 40 | 0.2 | 0.25 | 0.32 | 0.4 | 0.4 | 0.63 | 0.63 | 1.12 |
| 40 | 63 | 0.25 | 0.32 | 0.4 | 0.5 | 0.5 | 0.8 | 0.8 | 1.25 |
| 63 | 100 | 0.32 | 0.4 | 0.5 | 0.63 | 0.63 | 1 | 1.1 | 1.4 |
| 100 | 160 | 0.4 | 0.5 | 0.63 | 0.8 | 0.8 | 1.25 | 1.25 | 1.6 |
| 160 & over (Multiply by) | x .004 | x .005 | x .005 | x .008 | x .008 | x .010 |
Inch Tolerances (in)
| Nominal Dimension | A1 | A2 | A3 | A4 | |||||
|---|---|---|---|---|---|---|---|---|---|
| above | up to and including | Fixed | Closure | Fixed | Closure | Fixed | Closure | Fixed | Closure |
| 0 | 0.40 | 0.004 | 0.005 | 0.006 | 0.008 | 0.008 | 0.013 | 0.013 | 0.032 |
| 0.40 | 0.63 | 0.005 | 0.006 | 0.008 | 0.010 | 0.010 | 0.016 | 0.016 | 0.036 |
| 0.63 | 1.00 | 0.006 | 0.006 | 0.010 | 0.013 | 0.013 | 0.020 | 0.020 | 0.040 |
| 1.00 | 1.60 | 0.008 | 0.010 | 0.013 | 0.016 | 0.016 | 0.025 | 0.025 | 0.045 |
| 1.60 | 2.50 | 0.010 | 0.013 | 0.016 | 0.020 | 0.020 | 0.032 | 0.032 | 0.050 |
| 2.50 | 4.00 | 0.013 | 0.016 | 0.020 | 0.025 | 0.025 | 0.040 | 0.040 | 0.056 |
| 4.00 | 6.30 | 0.016 | 0.020 | 0.025 | 0.032 | 0.032 | 0.050 | 0.050 | 0.063 |
| 6.30 & over (Multiply by) | x .004 | x .005 | x .005 | x .008 | x .008 | x .010 |
Table 12. Summary of RMA Drawing Designations Extruded Rubber Products
| RMA Class | Dimensional Tolerance* Table 13 | CutLength Tolerance* Table 16 | SplicedLength Tolerance* Table 16 | MandrelCured* Table 20 |
|---|---|---|---|---|
| 1 | E1 | L1 | S1 | EN1 |
| 2 | E2 | L2 | S2 | EN2 |
| 3 | E3 | L3 | S3 | EN3 |
| - | - | - | - | - |
Table 13. Standard Cross-Sectional Tolerance
| RMA Class | 1 - High Precision | 2 - Precision | 3 - Commercial |
|
|---|---|---|---|---|
| Drawing Designation | E1 | E2 | E3 | |
| Dimensions (in Millimeters) | ||||
| Above | Up to and including | |||
| 0 | 1.5 | +0.15 | +0.25 | +0.4 |
| 1.5 | 2.5 | 0.20 | 0.35 | 0.50 |
| 2.5 | 4 | 0.25 | 0.40 | 0.70 |
| 4 | 6.3 | 0.35 | 0.50 | 0.80 |
| 6.3 | 10 | 0.40 | 0.70 | 1.00 |
| 10 | 16 | 0.50 | 0.80 | 1.30 |
| 16 | 25 | 0.70 | 1.00 | 1.60 |
| 25 | 40 | 0.80 | 1.30 | 2.00 |
| 40 | 63 | 1.00 | 1.60 | 2.50 |
| 63 | 100 | 1.30 | 2.00 | 3.20 |
| RMA Class | 1 - High Precision | 2 - Precision | 3 - Commercial | |
| Drawing Designation | E1 | E2 | E3 | |
| Dimensions (in Inches) | ||||
| Above | Up to and including | |||
| 0 | 0.06 | +0.006 | +0.010 | +0.015 |
| 0.06 | 0.10 | 0.008 | 0.014 | 0.020 |
| 0.10 | 0.16 | 0.010 | 0.016 | 0.027 |
| 0.16 | 0.25 | 0.014 | 0.020 | 0.031 |
| 0.25 | 0.39 | 0.016 | 0.027 | 0.039 |
| 0.39 | 0.63 | 0.020 | 0.031 | 0.051 |
| 0.63 | 0.98 | 0.027 | 0.039 | 0.063 |
| 0.98 | 1.57 | 0.031 | 0.051 | 0.079 |
| 1.57 | 2.48 | 0.039 | 0.063 | 0.098 |
| 2.48 | 3.94 | 0.051 | 0.079 | 0.126 |
Table 16. Cut Length tolerance for unspliced extrusion
| 1 - HighPrecision 2 -Precision 3 - Commercial | ||||
|---|---|---|---|---|
| Drawing Designation. | L1 | L2 | L3 | |
| Length (in Millimeters) | ||||
| Above | Up to and including | |||
| 0 | 40 | +0.7 | +0.04 | +1.6 |
| 40 | 63 | 0.08 | 1.3 | 2.0 |
| 63 | 100 | 1.0 | 1.6 | 2.5 |
| 100 | 160 | 1.3 | 2.0 | 3.2 |
| 160 | 250 | 1.6 | 2.5 | 4.0 |
| 250 | 400 | 2.0 | 3.2 | 5.0 |
| 400 | 630 | 2.5 | 4.0 | 6.3 |
| 630 | 1000 | 3.2 | 5.0 | 10.0 |
| 1000 | 1600 | 4.0 | 6.3 | 12.5 |
| 1600 | 2500 | 5.0 | 10.0 | 16.0 |
| 2500 | 4000 | 6.3 | 12.5 | 20.0 |
| 4000 | 0.16% | 0.32% | 0.50% | |
| Length (in Inches) | ||||
| Above | Up to and including | |||
| 1 | 1.6 | +0.03 | +0.04 | +0.06 |
| 1.6 | 2.5 | 0.03 | 0.05 | 0.08 |
| 2.5 | 4 | 0.04 | 0.06 | 0.10 |
| 4 | 6.3 | 0.05 | 0.08 | 0.13 |
| 6.3 | 10 | 0.06 | 0.10 | 0.16 |
| 10 | 16 | 0.8 | 0.13 | 0.20 |
| 16 | 25 | 0.10 | 0.16 | 0.25 |
| 25 | 40 | 0.13 | 0.20 | 0.40 |
| 40 | 63 | 0.16 | 0.25 | 0.50 |
| 63 | 100 | 0.20 | 0.40 | 0.63 |
| 100 | 160 | 0.25 | 0.50 | 0.80 |
| 160 | 0.16% | 0.32% | 0.50% | |
Table 18. Spliced Length Tolerances
| RMA Class | 1 - High Precision | 2 - Precision | 3 - Commercial | |
|---|---|---|---|---|
| Drawing Designation | S1 | S2 | S3 | |
| Millimeters | ||||
| Above | Up to and including | |||
| 0 | 250 | +302 | +3.2 | +7.1 |
| 250 | 400 | 4.0 | 7.1 | 8.0 |
| 400 | 630 | 5.0 | 8.0 | 9.0 |
| 630 | 1000 | 6.3 | 9.0 | 10.0 |
| 1000 | 1600 | 8.0 | 10.0 | 11.2 |
| 1600 | 2500 | 10.0 | 11.2 | 12.3 |
| 2500 | over | 012.5 | 12.5 | 16.0 |
| Inches | ||||
| Above | Up to and including | |||
| 0 | 10 | +.13 | +.25 | +.28 |
| 10 | 16 | .16 | .28 | .32 |
| 16 | 25 | .20 | .32 | .36 |
| 25 | 40 | .25 | .36 | .40 |
| 40 | 63 | .32 | .40 | .45 |
| 63 | 100 | .40 | .45 | .50 |
| 100 | over | .50 | .50 | .53 |
Table 20. Tolerances on Internal Dimensions of Mandrel-Supported Extrusions
| RMA Class | 1 - High Precision | 2 - Commercial | 3 - Non-Critical | |
|---|---|---|---|---|
| Drawing Designation | EN1 | EN2 | EN3 | |
| Nominal Dimensions (in Millimeters) |
||||
| Above | Up to and including | |||
| 0 | 4 | +0.20 | +0.20 | +0.35 |
| 4 | 6.3 | 0.20 | 0.25 | 0.40 |
| 6.3 | 10 | 0.25 | 0.35 | 0.50 |
| 10 | 16 | 0.35 | 0.40 | 0.70 |
| 16 | 25 | 0.40 | 0.50 | 0.80 |
| 25 | 40 | 0.50 | 0.70 | 1.00 |
| 40 | 63 | 0.70 | 0.80 | 1.30 |
| 63 | 100 | 0.80 | 1.00 | 1.60 |
| 100 | 160 | 1.00 | 1.30 | 2.00 |
| 160 | 0.6% | 0.8% | 1.2% | |
| Nominal Dimensions (in Inches) | ||||
| Above | Up to and including | |||
| 0 | 0.16 | +0.008 | +0.08 | +0.014 |
| 0.16 | 0.25 | 0.008 | 0.010 | 0.016 |
| 0.25 | 0.40 | 0.010 | 0.014 | 0.020 |
| 0.4 | 0.63 | 0.014 | 0.016 | 0.028 |
| 0.63 | 1.00 | 0.016 | 0.020 | 0.032 |
| 1.00 | 1.6 | 0.020 | 0.028 | 0.040 |
| 1.6 | 2.5 | 0.028 | 0.032 | 0.051 |
| 2.5 | 4.00 | 0.032 | 0.040 | 0.063 |
| 4.00 | 6.30 | 0.040 | 0.051 | 0.079 |
| 6.30 | 0.6% | 0.8% | 1.2% | |
Need parts held to a specific RMA class?
Send your drawing or dimensions — our engineers confirm the achievable tolerance grade, tooling and a path to production, usually within one business day.