The 1" Wilkins Model 350XL double check assemblies began production in 2010 and are currently still being produced. The 350XL is the lead free version of the model 350. They feature a lead free bronze carriage that holds a plastic body which houses the check assemblies. The plastic housing rests into the bronze carriage and is locked in with a wedge system. The device is an inline module check design. No special tools are required for servicing.