Includes 8 wheels, 16 Hybid Ceramic Bearings, 8 8mm Spacers, and 8 6mm Stepped Spacers (You only need 1 set of spacers depending on your skates, we inclue both as a courtesy). These wheels are perfect for outdoor skating, and utilize the standard size 608 bearing hub. The 89a Durometer rating provides a long lasting, rock hard feel. For that reason, 89a is the most popular outdoor durometer rating. The added longevity of a harder wheel gives you more bang for your buck. Amp Hybrid Ceramic bearings are like stimulants for your wheels. With this bearing you get the precision of ceramic and the durability of steel balls. The single Ceramic ball cleans debris and cools friction allowing for a longer lasting bearing.