From Limtech

Limtech Incorporated is a leading designer and manufacturer of standard o-rings, rubber seals, and custom sealing devices. Whatever size you are looking for we have it.

An O-Ring is a torus, or doughnut shaped object, with a circular cross section. Usually made from an elastomer, although such materials as metal or plastic are sometimes used. All sizes are available in various elastomers: Silicone, EPDM, Neoprene, Viton, Buna, Nitrile and Teflon.

Limtech has a standard line of silicone o-rings, as shown in the chart below. They can be provided in durometers ranging from 20 to 80 shore A to best fit your needs.
Limtech #	O-ring #	Inside Diameter	Outside Diameter	Cross Section
L-003	003	.056	.176	.060
L-004	004	.070	.210	.070
L-005	005	.101	.241	.070
L-006	006	.114	.254	.070
L-007	007	.145	.285	.070
L-008	008	.176	.316	.070
L-009	009	.208	.348	.070
L-010	010	.239	.379	.070
L-011	011	.301	.441	.070
L-012	012	.364	.504	.070
L-013	013	.426	.566	.070
L-014	014	.489	.629	.070
L-015	014	.551	.691	.070
L-016	016	.614	.754	.070
L-017	017	.676	.816	.070
L-018	018	.739	.879	.070
L-019	019	.801	.941	.070
L-020	020	.864	1.004	.070
Tolerance :ID/OD + or - .005
Cross section + or - .003