I know that the most skateboard bearing is 608(8x22x7mm), but there is also some skateboards choosing 10mm skateboard bearing, that is 6900 skate bearing.
6 of 6900 bearing represents that it is a deep groove ball bearing, 9 refers to a series of deep groove ball bearing and 00 represents that the inner diameter size is 10mm. The size specification of 6900 bearing is 22mm (outside diameter), 6mm (width) and 10mm (inner diameter). Sometimes we write 6900 bearing like 10x22x6mm.
The total inline skate bearing 10mm comprises several balls, two rings, one retainer (nylon or steel material) and two seals. Seals’ material can be mental or rubber seals. If you choose mental seals, we can call them 6900zz. If you choose rubber, we can call them 6900-2rs.
Generally speaking, the material of 6900 10mm skate bearing is chrome steel, but we can also provide some special 10mm inline skate bearing materials, including stainless steel and ceramic.
699 2rs Hybrid Ceramic Bearings For Bicycle Wheel Hub