IDEAL patented No-Hub Couplings are engineered to connect no-hub cast-iron pipe in application replacing the less-efficient hub & spigot material. The couplings consistence of an elastomeric compound gasket(ASTM C-564)housed inside a 301 stainless steel corrugated shield Depending on the size of the Shield, (2) or (4)301 stainless steel clamps surround the shield and provide the sealing force. The 5/16" hex-head screws are made from 305 stainless steel.