These x ends are designed to minimize Z axis binding. They do that by adding a second set of bushings into the X axis idler. These bushings allow the X shafts to move a small amount in the X direction while remaining rigid in the Y & Z directions. This allows the distance between the two x-ends to increase and decrease as the height changes, helping to minimize Z axis binding. Note: The leadscrews these weere designed to be compatible with are no longer available. You can still use these with a printable nut adapter such as these: http://www.thingiverse.com/thing:23326Update: Added a variant to use with select 3-hole lead screws such as the new ones sold by Maker's Tool Works ( http://store.makerstoolworks.com/motion/z-axis-lead-screw-and-nut-set-of-2/ ) and the PBC leadscrews sold by Trinity Labs. These files are names X End [part] for MTW Leadscrew. Source file is also updated to the latest versions.Uses eight SDP self aligning bushings, available from Stock Drive Products (For example http://shop.sdp-si.com/catalog/product/?id=A_7Z41MPSB10M, also available from http://store.makerstoolworks.com). Four in the idler end for the anti-binding feature, and four for the Z axis bushings. It is compatible with either 8 or 10mm bushings in either bronze or PTFE-filled acetal. Use bronze with precision shafting or PTFE with drill rod for best results.The motor end clamp and the delrin nuts all attach with M5-20mm screws and nuts.Update: Added an alternate version that clamps on both ends. This eliminates the anti-binding benefits, but is easier to print reliably. With the easily adjustable Z axis shaft spacing of the MM 1.5, the non binding features are less important than they were on earlier versions. This version uses the same clamp as the motor end.Update: Added an optional lead nut adapter to use with select 3-hole leadscrews such as the new ones sold by Maker's Tool Works ( http://store.makerstoolworks.com/motion/z-axis-lead-screw-and-nut-set-of-2/ ) and the PBC leadscrews sold by Trinity Labs.