The 6" Wilkins 350ASTDA is a double check detector assembly began production in 2011 and is still currently being produced. The body is constructed of stainless steel. Check assemblies are a plastic cam check design and springs are self contained. Spring tension does not need to be released to replace rubber discs. Retainer clips hold the checks in place. The 350AST uses a single victaulic clamp style cover. The 350AST uses grooved connections between the body and gate valves. The bypass device is a 3/4" 950XL or 3/4" 950XLT2. No special tools are required for servicing.