BONES SWISS Ceramics are simply THE BEST performance bearings money can buy! A personal favorite of RollerSkatin.ca :D. Quality Roller skate bearings by the best name in Roller Skate Bearings. Highly polished Cerbec ceramic balls don't retain heat like steel balls therefore run smoother and more consistently under pressure! Ceramic balls are smoother, last longer, and increase speed by 4 MPH. Non contact, removable rubber shields. Available in 7mm (627) or 8mm (608) size. Package of 16 precision sealed bearings.