3627-4008-3212, 8mm Groove, 8mm REX™ ID Bearings, 32mm Diameter U-Wheel - 2 Pack

Designed to support linear motion with Rail-Channel, this polycarbonate U-Wheel features two pressed-in 8mm REX™ bearings for smooth rotation on 8mm REX™ profile components---such as shafting or standoffs. 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.