Flip Skateboard bearings mount your wheels to the axle. Keeping your bearings clean and in good condition is essential to a smooth ride. Make it easy on yourself by starting with high-quality Flip Skateboards bearings. Sold in sets of 8 bearings to complete four skateboard wheels for one skateboard, two bearings mount each skateboard wheel to its truck axle. The industry standard size is 608 with an 8 mm bore, a 22 mm outer diameter and a width of 7mm. Bearings rated under the ABEC scale are typically called "precision bearings", and they are rated with a number from 1 to 9. Higher ratings are assigned to bearings manufactured against a higher standard of precision (high number = tighter tolerances = more expensive bearing). Higher numbers are not necessarily better for skateboarding, as the ABEC rating only measures tolerances which do not necessarily apply to skateboards.