This is a single Phil Wood 6902 Cartridge Bearing. Compatible with Phil Wood Cassette and Rear Hubs. Features: Phil Wood and Company is credited for pioneering the first production sealed bearing cycling components 100% filled with Phil Waterproof Grease for maximum durability Bearings with an "X" have the same seals as those specified for submersible motor/pump bearings Specs: Bearing: 6902X ID X OD X W Mm: 15x28x7