I bought 3 of these, ( nema 34 R&P mounts) for my joe's 4X4 cnc router. I can not say enough good things about these. Ahren had done a excellent job at designing a top notch, quality product here. These mounts work flawlessly. My motors mounted without any problems. The tesioners work very good at keeping my pinion meshed with the racks through the travel of my cnc router. Also, when the machine is running, the rack and pinion run very quite. I would highly recommend these to anybody that is at all thinking about them. One more thing, I am getting rapid speeds of 1550IPM with this system. Not bad for my first time DIYer build. I will most likely be running in the 400 to 600IPM rapids though, 1550 is a little scary for me. :-) Thank you Ahren for the quality product. Randy Rating: [ of 5 Stars!]