Hexagon black pvd stainless steel plugs with a flat front and an adjustable "O" ring that is made from both stainless steel and silicone in the inside, so it is easily adjustable. Hallow interior. Single flared. Choose your size from 2G (6mm) - 5/8" (16mm). Made from black pvd on 316L stainless steel. Sold in pairs (2pcs).