Gravity water filling cap for RVs. Made from high quality PP, it is strong, wear-resistant, not easy to break, and provides a long service life. Outlet hole design. The hatch lock uses an outlet hole design to prevent vacuum in the water tank during filling, allowing you to add water smoothly and with less effort. Dust protection. The water fill hatch lock includes a dust protection design, is easy to clean, and effectively prevents dust and other foreign objects from entering the tank. With locking key. The inlet of the water fill hatch is lockable and includes 2 keys, preventing unauthorized opening of the water filling port. Use scenarios - On long road trips, quickly and securely fill the fresh water tank without vacuum issues or spills. - In RV rental fleets or service vehicles, control access to the fill port with the included keys for security. - At campgrounds or remote sites, keep dust and debris out of the tank while maintaining easy cleaning and maintenance.