The Rubber Manufacturers Association (RMA) has developed standard tolerance specifications for rubber products with permissible ranges for clarity between user and provider/manufacturer across a wide range of industries. These are helpful when designing and manufacuring elastomer components. You can review these RMA tolerance tables below for your design considerations.

Metric tolerances (mm)

Nominal Dimension		A1		A2		A3		A4
Above	Up to and including	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 (mm)

Nominal Dimension		A1		A2		A3		A4
Above	Up to and including	Fixed	Closure	Fixed	Closure	Fixed	Closure	Fixed	Closure
0	0.4	0.004	0.005	0.006	0.008	0.008	0.013	0.013	0.032
0.4	0.63	0.005	0.006	0.008	0.01	0.01	0.016	0.016	0.036
0.63	1	0.006	0.006	0.01	0.013	0.013	0.02	0.02	0.04
1	1.6	0.008	0.01	0.013	0.016	0.016	0.025	0.025	0.045
1.6	2.5	0.01	0.013	0.016	0.02	0.02	0.032	0.032	0.05
2.5	4	0.013	0.016	0.02	0.025	0.025	0.04	0.04	0.056
4	6.3	0.016	0.02	0.025	0.032	0.032	0.05	0.05	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
4	–	–	–	–

Table 13. Standard Cross-Selection Tolerance

RMA Class		1 – High Precision	2 – Precision	3 – Commercial
Drawing Designation		E1	E2	E3
Dimensions (in Millimeters)
Above	Up to
0	1.5	0.15	0.25	0.4
1.5	2.5	0.2	0.35	0.5
2.5	4	0.25	0.4	0.7
4	6.3	0.35	0.5	0.8
6.3	10	0.4	0.7	1
10	16	0.5	0.8	1.3
16	25	0.7	1	1.6
25	40	0.8	1.3	2
40	63	1	1.6	2.5
63	100	1.3	2	3.2

RMA Class		1 – High Precision	2 – Precision	3 – Commercial
Drawing Designation		E1	E2	E3
Dimensions (in Inches)
Above	Up to
0	0.06	0.006	0.01	0.015
0.06	0.1	0.008	0.014	0.02
0.1	0.16	0.01	0.016	0.027
0.16	0.25	0.014	0.02	0.031
0.25	0.39	0.016	0.027	0.039
0.39	0.63	0.02	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

RMA Class		1 – High Precision	2 – Precision	3 – Commercial
Drawing Designation		E1	E2	E3
Dimensions (in Millimeters)
Above	Up to
0	40	0.7	0.04	1.6
40	63	0.08	1.3	2
63	100	1	1.6	2.5
100	160	1.3	2	3.2
160	250	1.6	2.5	4
250	400	2	3.2	5
400	630	2.5	4	6.3
630	1000	3.2	5	10
1000	1600	4	6.3	12.5
1600	2500	5	10	16
2500	4000	6.3	12.5	20
4000		0.16%	0.32%	0.50%

Length (in Inches)
Above	Up to
0	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	0.1
4	6.3	0.05	0.08	0.13
6.3	10	0.06	0.1	0.16
10	16	0.8	0.13	0.2
16	25	0.1	0.16	0.25
25	40	0.13	0.2	0.4
40	63	0.16	0.25	0.5
63	100	0.2	0.4	0.63
100	160	0.25	0.5	0.8
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	±302	±3.2	±7.1
0	250	4	7.1	8
250	400	5	8	9
400	630	6.3	9	10
1000	1600	8	10	11.2
1600	2500	10	11.2	12.3
2500	over	12.5	12.5	16

Inches
Above	Up to
0	10	0.13	0.25	0.28
10	16	0.16	0.28	0.32
16	25	0.2	0.32	0.36
25	40	0.25	0.36	0.4
40	63	0.32	0.4	0.45
63	100	0.4	0.45	0.5
100	over	0.5	0.5	0.53

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
0	4	0.2	0.2	0.35
4	6.3	0.2	0.25	0.4
6.3	10	0.25	0.35	0.5
10	16	0.35	0.4	0.7
16	25	0.4	0.5	0.8
25	40	0.5	0.7	1
40	63	0.7	0.8	1.3
63	100	0.8	1	1.6
100	160	1	1.3	2
160		0.60%	0.80%	1.20%

Nominal Dimensions (in Inches)
Above	Up to
0	0.16	0.008	0.08	0.014
0.16	0.25	0.008	0.01	0.016
0.25	0.4	0.01	0.014	0.02
0.4	0.63	0.014	0.016	0.028
0.63	1	0.016	0.02	0.032
1	1.6	0.02	0.028	0.04
1.6	2.5	0.028	0.032	0.051
2.5	4	0.032	0.04	0.063
4	6.3	0.04	0.051	0.079
6.3		0.60%	0.80%	1.20%

RMA Tolerance Table