How to test the size of O-ring?

Standard o-rings can be measured with a conical die, put the o-rings on cone, using gravity fall, can measure the inner diameter of the o-rings, as for the wire diameter, can be used three coordinate measuring, originally o-rings is elastic, the precision is not very high, after drawing size change is very big, if think vernier caliper measurement is not accurate, I'll just use the CMM, but I personally don't think it's necessary.

Test tools:

Sealing ring inner diameter measuring ruler, O-type rubber ring inner diameter measuring ruler

Sealing ring diameter scale: used for the average inner diameter measurement of flexible materials and steel materials and precision measurement of the average inner diameter or outer diameter of O type rubber sealing ring.

Application: O-ring, vacuum rubber washer, rotary seal, etc.