Features:Features a 360 degree swivel mounting plate attached to a double wheel roller system.Two-Hole, metal and Flange-mounted 16mm ball bearing resting on individual support bearings and is Perfect for most industrial transfer applications.Ball transfer unit can also be used in a variety of non-industrial applications, including retail store displays and airport luggage transfers.Ball support cup is hardened and plated, protective cover assures low torque and longevity.Ball Transfer Unit is perfect replacement for your broken one on your office chair.Specifications:Model Number: -15AType: Window RollersSurface treatment : Zinc PlatingModel : -15A ,5/8-ALength : 50mmWidth : 30mmHeight : 2mmMounting Hole Pitch : 40mmFixing Hole Distance : 4mmBall Diameter : 15.875mm (5/8 inch)Single Load : 10kg (Max. 20kg)Single Weight : 43gColor: SilverMaterial: carbon steelPackage Contents:20 * Ball Transfer UnitOnly the above package content, other products are not included.Note: Light 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.