This is a single Phil Wood 6000 Cartridge Bearing. Compatible with Suntour, FSA, Formula Track 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: 6000 ID X OD X W Mm: 10x26x8