This is a first cam check assembly for the Wilkins 350, 350A, 350DA, 350ADA, 450, & 450DA series assemblies. This is a complete first cam check. The check is held in place by a plastic retainer ring. Use caution when removing the retainer ring as they often break. Replacement retainer ring is included. Genuine Zurn/Wilkins repair parts. No special tools are required for servicing.