Silicone bronze cast body. Silicone bronze cast poppet. Features include buna-n O-ring, stainless steel spring, stainless steel washer, and stainless steel locknut. Working pressure of 400 P.S.I. No. 542SB: Type: Spring Loaded, Size: 1″, Material: Silicone Bronze, Pressure Rating: 400 psi, Temperature Rating: Cool Water Only No. 543SBCHECK: Type: Spring Loaded, Size: 1-1/4″, Material: Silicone Bronze, Pressure Rating: 400 psi, Temperature Rating: Cool Water Only