Needed to make a good Y Axis Endstop for the Acrylic Prusa i3 Mechanical Endstop V1.2 http://reprap.org/wiki/Prusa_i3 It fits neatly and the endstop touches the acrylic bed, allowing max travel. 3 x 3mm Cup head @ 16mm Long 3 x 3mm Nuts 3 x 3mm Spring Washers Don't over tighten the Cup Head between the Rods, this is just to add a bit of tension, a small tighten is all you need. If need be add some 8mm nuts to either side, depending on the fit on your rods.. I found it Not necessary to do so. It should be OK on the Aluminium Laser Cut Y Axis as well Cup Heads can be swapped for Phillips, as seen in picture.... If your machine is already built, you mat want the Split variety here: http://www.thingiverse.com/thing:928883 If you use it, please click the like :-)