This is a Centre Axis for an X/Y Cartesian 3D Printer - similar to the Ultimaker.This is designed to hold the LM8UU or similar Linear Bearings - it will fit 2 in the X direction and 2 in the Y direction - and slide perfectly on an 8mm CNC Shaft.I have also included the Sled for the X and Y shaft - used at both ends of the central shafts - this is then joined to the Drive belt at both ends for Smooth and fast X/Y transitions. Timing belt and shaft joining is done with simple aluminium brackets over the top to form pressure against belt and shaft.