Some users prefer this brand of ground joints as the unique Viton O-ring seal eliminates air or steam leaks when hand tightened (the stems are interchangeable with traditional Ground Joint Couplings, including spuds with copper or polymer seats). The O-ring passes 1,000 hour MIL-H-29210 steam test and is protected within a groove on the face of the machined stem (the spud does not require a plastic polymer or copper seat).