Strataflo® 300-100 1" 300 Bronze Spring Check Valve with Buna-S Rubber Poppet, 13 GPM. The No. 300 check valve is made of a one-piece cast brass body. Designed to operate in any position, a sensitive spring has been added to close the poppet automatically. The rubber poppet is fully-formed around a solid steel insert to provide greater strength in commercial applications. Each valve is tested twice for casting integrity and backflow prevention. All valves are 100% American-Made and built to last.