Features a 360 degree swivel mounting plate attached to a double wheel roller system. Two-Hole, metal and Flange-mounted ball bearing resting on individual support bearings and is perfect for most industrial fer applications. Ball fer unit can also be used in a variety of non-industrial applications, including retail store displays and airport luggage fers. Ball support cup is hardened and plated, protective cover assures low torque and longevity. Ball fer Unit is perfect replacement for your broken one on your office chair. Specifications: Surface treatment : Zinc Plating Model : CY-15A Length : 50mm Width : 32mm Mounting Hole Pitch : 40mm Fixing Hole Distance : 4mm Single Load : 10kg (Max. 15kg) Colour: silver Material: carbon steel Size: Ball diameter: 5/8 inches, about 15.8mm, height: 21mm Package Contents: 20 x Roller Ball fer Bearings / 5 x Roller Ball fer Bearings Only the above package content, other products are not included. Note: Light shooting 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.