Fitted with a steel ball bearing, the wheels enable simple linear motion, and moveable framework to be constructed. The wheels are available plain or with centre guide for motion in an XC (11 mm) T-slot. Both wheels come complete with spacer sleeves which make it possible to mount directly into the T-slot. Alternatively a yoke mounting is available to fit wheels to the end of XC44 beams (not XCBL).,Wheels bore size (mm) = 8.4 ,Yoke centre height (mm) = 42,Yoke width (mm) = 44