Full Ceramic Peekaboo5 bike bearing kits are specially designed for competitive on-road or off-road riders looking for the absolute least amount of rolling resistance. Peekaboo5 bearings have high precision, grade 5, silicon nitride ceramic balls, Zirconia ceramic ABEC 5 races, a high speed Peek retainer, no friction peek seals and Boca's exclusive low friction grease. Full ceramic bearings are virtually frictionless and roughly half the weight of a steel bearing.