This is the most popular swiss rated bearing to fit skateboard wheels, inline wheels, caster wheels, scooter wheels. The bearing size is 608 and has 1 protective outer seal, and one open side for easy servicing. The outer seal provides an effecting barrier against contamination. The bearing retainer (ball cage) is made of molded nylon. This retainer provides smooth and efficient bearing roll. These bearings are manufactured to precision standards, and do not carry an abec rating.