This is a first cam check assembly for the Wilkins 375, 375A, 375DA, 375ADA, 475, & 475DA 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.