[Material]: This ball bearing retainer is made of steel, which is of good quality, durable and high strength. [Size] : Outer Diameter: 37mm / 1.45"; Inner diameter: 27.5 mm/1.08". One package includes: 4 bicycle ball bearings [Product features]: It has 20 stainless steel balls inlaid in the retainer, which is firm and does not fall off, and the balls are lubricated and rotated. [Use]: It is suitable for replacing the headset bearing of the bicycle. Suitable for regular bikes, mountain bikes, low rider bikes, bouncy bikes. [Precautions]: Before purchasing, please confirm whether the size of your bicycle accessories matches this bearing.