Features: 90mm wheels are designed for reliable performance at a greater value 90mm/SG9 bearings/8mm spacers 90mm/84A wheels are extra-high upgrade value wheels Easy replacement SG9 Bearings and Spacers SG9 silicone/grease helps limit friction and increase speed Wheel kit includes: (8) 90mm wheels, (16) SG9 bearings, and (8) 8mm spacers preassembled for replacing wheels