The 6" Ames Maxim series M-400 Reduced Pressure Zone (RPZ) began production in 2000 under the Hunter name. In 2002, Ames bought the rights off of Hunter and is still manufacturing the devices. The body is constructed of stainless steel. Similar to the Maxim Series, the Maxim features larger internal parts to increase flow rates. It is 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. The Maxim uses two self contained cam checks that use a tri-link check mechanism. Numerous repair parts are available for the Maxim series devices, including rubber parts and complete parts. The relief valve can be unthreaded from the body for ease of service. The Maxim uses an external relief valve sensing line. There are no special tools required for service.