Specification: Product Name: 608 ABEC-9 Black Cover Scooter Bearing Outer diameter: 22mm0.87inch Inner diameter: 8mm0.31inch Thickness: 7mm0.28inch Weight: 12gpiece Material: The outer ring is made of bearing steel, and the inside is made of TH glass fiber reinforced phenolic resin, which is strong and durable Uses: Scooters, roller skates, cars, etc.