U-Wheel (8mm Groove, 4mm ID Bearings, 32mm Diameter) - 2 Pack

Designed to support linear motion with Rail-Channel, this polycarbonate U-Wheel features two pressed-in 4mm ID bearings for smooth rotation on M4 screws as well as 4mm diameter shafting. While one bearing is flush with a side of the wheel, the side with the opposite bearing offers a space for easy carriage-height adjustment and clearance for hardware.

You can run U-Wheels on lengths of Rail-Channel by placing two parallel lines of multiple U-Wheels 96mm apart from each other.