King Brothers Inc. KC-0500-S 1/2-Inch Slip PVC Schedule 40 Spring Check Valve, White EPDM seals Meets/exceeds ASTM schedule 40 dimensional and material standards Made of high-impact PVC Type II material Spring and stem: 18-8 (302 series) stainless steel 150 psi working pressure (tested to 500 psi static @ 73F)