100pcs Watch Case O Ring Round Gasket Dia 12-30mm Rubber Seals Kit Repair Tool The set contain sizes from 12mm to 30mm ... Made of rubber material and of fair quality. This is a rubber O-Ring round watch gasket that keep your watch water resistant. The set contain 100pcs assorted size & thickness that fit all kind of men and ladies watches. This is excellent for most watches, especially if you are doing watch battery replacement. Gaskets will stretch a couple of millimeters and will work on watches of shapes other than round.