S6903-2RS ABEC-5 Ball Bearing Stainless Steel and Ceramic Balls 17 x 30 x 7 mm S6903-2RS Stainless Steel Ceramic Balls ABEC-5 quality, this is a popular size that could be used in many application that uses this size 17mm x 30mm x 7mm, each bearing has 2 Rubber Seals to protect the bearing from dust or any possible contamination, also bearing is pre-lubricated with grease.