Strataflo® 5300-400 4" 5300 Aluminum Check Valve with Buna-S Rubber Poppet, 204 GPM. The No. 5300 is an aluminum check valve manufactured from a one-piece cast ASTM-A356 body, with all other internal components of stainless steel. The high-strength body also has an anodized finish for added corrosion resistance. The rubber poppet is fully-formed around a solid steel insert to provide for greater strength in commercial applications. Each valve is tested twice for casting integrity and backflow prevention. All valves are 100% AmericanMade and built to last.