This is V2 of my Solidoodle 2 Anti-Backlash Assembly. It's fairly similar to identical to my first version, but I've reduced the overall height so there's a little more space between the top of the nut ant the top of the z-axis screw when the bed is at the top of the z-axis. The second photo shows the height differential, with V1 on the left and V2 on the right.The spring I'm using has a 0.825 O.D., 0.725 I.D, and 0.05 wire thickness. It's approximately 1.2 inches free length, and 0.300 compressed length. This particular spring was selected simply because it was all my local hardware had on hand that met my needs. Century Spring (centuryspring.com) carries a similar spring that looks like it will work nicely: part no. S-799. Unfortunately, they've got a $40 minimum order so I haven't tried yet. When printing the upper spring retainer, I've been printing with the hex side down, and using support material inside the hex. It might be possible to print without support material, but I haven't tried it yet. I the future, I may try creating chamfer at the bottom of the hex instead of a flat surface in order to see how it prints without support material. When assembling the two halves, I usually take a small file to the side mating surfaces of the cutaways. Ideally, you want the two halves to fit together and be able to slide vertically without binding.