Quote Originally Posted by lysander View Post
Buna-N (aka, nitrile or NBR), 70 Shore A hardness, 0.071" thick.

EDIT: While your uptown buy a 17/32 punch.
Nitrile, yes, thank you. Don't know why I was thinking about neoprene as it's pretty spongey. Mechanic I know has a punch set that I can use. Thanks again.