High-speed ball-bearings produced specifically for XRAY. ID x OD x thickness (") = 1/4" x 3/8" x 1/8". Number of 2 pieces. Top-quality specialist ball-bearings for super-free, super-smooth procedure. These best quality ball-bearings are degreased and carefully oiled with AeroShell Fluid 12 oil for optimum smoothness, endurance, highest threshold and maximum performance.