ASTM A217 C5 Check Valve is a valve made from a 5% chromium and 1/2% molybdenum alloy, designed for high-temperature refinery services. These valves are widely used in industries like oil and gas, petroleum, offshore, and onshore oil drilling. Functioning as non-return valves, they allow fluid flow in only one direction through two openings: one for entry and one for exit. Check valves come in various types suited for diverse applications, including common household items.