●Materil: These ball bearings are made of bearing steel for low noise and have good anti-rust performance, long service life. ●Rubber side seals: They are lined with rubber to prevent ingress of contaminants and save lubricant. ●Application: Fit for all kinds of hybrid/comfort bike, road bike,industrial equipment, micro motors, small rotating motors, office equipment, etc. ●Rolling element: Can maintain spacing between moving parts to reduce rotational friction and support radial and axial loads. ●Note: Please refer to the picture and select right type of bearings before your order