The Ring Check® valve’s design has an in-line, spring assisted self-closing disc. The two-piece valve features a stainless steel stem and resilient PTFE disc. The valve is recommended for domestic hot and cold water, HVAC (condensers, chilled water, hot water heating). As an addition to the NIBCO® Press System®, the press end connections make the Ring Check quick and easy to install. he.When properly crimped a unique "N" witness mark is clearly visible. Please refer to NIBCO technical datamore sheets and catalogs for engineering and installation information. NIBCO® Press System® applies the proven performance of press technology to NIBCO valves and fittings -- the most specified flow control products in the industry. The NIBCO® Press System® features a full range of precision engineered copper fittings, bronze valves, accessories, pressing tools, jaws and chains. NIBCO® Press System® valves are backed by a 5-year limited warranty. less