There are all kinds of materials, that these o-rings are made out of, so which is the best? I tried some from a hardware store and they just did not seem the same on shock shaft. Checked Grainger online store and found lots of different materials these are made out of, and hardness were different also.

For what usage?

I did a edit on the post Slider

If there for the shocks. it depends on what oil you use. petroleum based or synthetic.

I prefer high temp silicone o rings.