Unlike traditional O-rings, hydrogenated nitrile butadiene rubber (HNBR) is a specialty-purpose elastomer that boasts a great deal of strength and retention in the face of heat, oil and chemical exposure. HNBR sealing elements are primarily geared toward gas applications, from natural and propane to mixed and manufactured gases, along with oils and lubricants. ProPress sealing elements are designed to deliver the most durable connection for pipe fittings across a broad range of plumbing applications. ProPress HNBR sealing elements may NOT be installed in ProPress systems that require ANSI/CSALC-4 approval for natural gas or propane gas. Approved to the most codes and standards of any other fitting system (IPC, UPC and NSF included) and with more than 400 different fitting configurations to suit virtually any type of plumbing or HVAC job, Viega ProPress is the top choice of professionals around the globe.