Enduro ABEC 5 pro scooter bearings are some of the best on the market. Made from Grade 5 Chromium Steel balls which are 5/1,000,000" from being perfectly round. High carbon Chromium alloy races are hardened to R62. Nylon retainers w/ graphite are virtually friction-less and provide constant lubrication. Pricing is for a set of 4, bearing spacers are sold separately.