Model NO. :608 (it can option) 1.Bearing material:carbon,chrome,iron,ect 2.Type: 2RS ZZ ,Z ,RS,OPEN 3.Size: 8*22*7mm deep Groove Ball Bearing: Deep groove ball bearing mainly take radial load as well as take moderate axial load. With less coefficient of friction, high limiting speed, large size range and variations of structure, they are suitable for precision instruments, low noise motors, ...