This listing is for 4 piece/s.A needle roller bearing is a special type of roller bearing which uses long, thin cylindrical rollers resembling needles. Ordinary roller bearings' rollers are only slightly longer than their diameter, but needle bearings typically have rollers that are at least four times longer than their diameter. Like all bearings, they are used to reduce the friction of a rotating surface. Needle bearings have a greater surface area in contact with the races, so they can support a greater load. They are also thinner, so they require less clearance between the axle and the surrounding structure. Specifications Inside Diameter: 12mm Outside Diameter: 16mm Roller Bearing Type: Needle Race Width: 10mm Bore Type: Parallel Material: Metal Static Load Rating: 6.4kN Cage Material: Sheet Steel Number of Rows: 1 Dynamic Load Rating: 4.84kN End Type: Open Fatigue Limit Load: 710N Maximum Speed - Grease: 14000rpm Maximum Speed - Oil: 20000rpm