X-ends for holding 20x20 extrusion 3 hole delrin/lm8uus

x-ends compatible with the 3-hole delrin lead-screw nuts.

These x-ends don't hold x-rods, they hold a single 20x20 extrusion.

both ends have an integrated bolt holder meant to interface with a z-endstop held in the lower part from http://www.thingiverse.com/thing:28425

By the way these are intended for 605zz idler bearings, you'll have to enlarge the hole either before or after printing if you intend to use 608zzs.