SFR2-5ZZ Flanged Stainless steel Ball Bearing with Ceramic Balls 1/8" x 5/16" x 9/64" inch SFR2-5ZZ Flanged Stainless steel Ball Bearing with Ceramic Balls, each bearing has 2 metal shields to protect the bearing from dust or any possible contamination, Ceramic Balls are the highest standard of balls that can make your bearing live at least 5 times more than any other bearings.