Engineered specifically to protect bearings from the elements during all trailer operations. Takes the worry out of submerging your wheel hubs during launching and loading of boats. A unique coiled stainless steel spring combined with a neoprene seal maintains grease under constant pressure when filled. A built-in outlet allows surplus grease to escape if the hub is over filled or excessive pressure occurs. Extended grease fitting indicates full or that additional grease is needed. The integral flange allows for simple installation and removal. Molded polycarbonate construction provides exceptional impact resistance and eliminates corrosion caused problems.