Watts 757 Series Double Check Valve Assemblies began production in 2000 under the Hunter name. In 2002, Watts bought the rights off of Hunter and is still manufacturing the devices. They are available in sizes 2 1/2 - 10" and are constructed of stainless steel. The 757 Series has become a top seller of Watts due to the light weight design and short lay lengths. It is also offered in a number of configurations with many valve options. To access the check assemblies there is a stainless steel sleeve that will slide open. On the 2 1/2 - 6" you must unthread the #3 test cock then slide the cover. 8 - 10" uses two Victaulic clamps to hold the stainless sleeve. The 757 uses two self contained cam checks that use a tri-link check mechanism. There are no special tools required for service.