Powerful magnets ensure that each delicate nip is tightly squeezed between the two sides of the clamp. You decide just how much painful pressure they can handle? Put them in the freezer to cool things down or in a bowl of hot water to fire things up! Made from sleek aluminium, they are totally body-safe, hypoallergenic and easy-to-clean.Product dimensions0.39" x 0.39" x 1.38".Product diameter0.39".Waterproof. Phthalate free. Materials: Aluminum.