Single row deep groove ball bearings. Have 2 metal to protect the bearing from dust or any possible contamination. These bearings are pre-lubricated with grease. Package Content: 100 x deep groove ball bearings Only the above package content, other products are not included. Note: Light reflection and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is +/- 1-3cm.