I've been working to improve the print quality of my printer. After trying everything I could think of, someone mentioned that the flexible metal couplers can compress and stretch, resulting in Z artifacts. So I decided to replace them with stiff couplers. This is a replacement stiff coupler between a 5mm and 8mm shaft, as found on the MendelMax 2.0. I use these in conjunction with OhmEye's Z isolators: https://www.dropbox.com/sh/3uyotd400xp2ef5/2pLnjCypcV/STLs/Z%20Isolators/ohmeye_mm2_isolator_release%202x.STL With this combination, my print quality is the best I've had so far. If your stepper motors have a flat (as most do), print two of each part. Otherwise print four of the Z_Split_Coupler part. Then use a pair of M3 x 16 screws and M3 Nyloc nuts for each coupler to hold them together. Using Nyloc nuts instead of regular M3 nots will allow them to stay tight, even with all the motion of the Z axis.