VELOCITY PRECISION MADE ABEC 9 BEARINGS PROVIDE TOP PERFORMANCE AND TOP DURABILITY. S td size 608rs (8x22x7mm). Fits all stunt push scooter wheels, skateboards Inline,derby & roller skates. Bearings are rated on the abec scale from 1 to11 using only odd numbers and are ranked by how smooth they areand how much friction they produce.