These high-performance hubs are designed to ensure smooth running for up to 100,000 miles without requiring maintenance. A completely sealed lubrication chamber bathes the bearings in a lithium complex grease fortified with rust and oxidation inhibitors. When maintenance IS required, Vortex hubs make it easy. Just unscrew the threaded cap and pump fresh grease into the easily accessible external lubrication port fitting. The one-way flow pushes out the old grease while flushing the entire chamber with fresh grease. Backed by a 1 year parts & labor and 5 additional years parts warranty.