I went to my LHBS to pickup some new caps as the old ones are worn. They no longer have Cooper's caps but instead have LD Carlson white caps. They thought they'd fit but weren't sure. I'm comparing them to the Cooper's caps and there is an extra thread on the inside of the cap. I thought I'd better check on here to see if anyone else has used them.
They're 28mm bottle caps for 16oz PET bottles.