1. Deep groove ball bearings 2. Widely used, economical and standard bearing 3. Less friction, higher speeds and durability 4. Special non-contact double rubber seals to seal out dirt while providing friction-free performance 5. Easy installation and replacement Color: black Material: steel Size: about 5 x 10 x 4 mm Package Contents: 40 x Bearing Only the above package content, other products are not included. Note: Light reflection and different displays may cause the color of the item in a little different from the real thing. The measurement allowed error is +/- 1-3 cm.