We supply O-rings in various metric and inch standard sizes, the sizes are specified using the inside diameter and cross section diameter (thickness) of the O-rings.
The standard sizes depend on where you’re from. For instance, in the US the most common standard inch sizes are per SAE AS568C specification (e.g AS568-214)
Whereas the UK also has standards sizes known as BSsizes, typically ranging from BS001 to BS932.
ISO 3601- 1:2008 contains the most commonly used standard sizes, both inch and metric, worldwide. However, there are also several other size specifications.
Shore hardness can be between 40IRHD to 95 IRHD and in some instances coloured rings can be manufactured. Variants on the o ring would be the square section ring and the quad or X ring.