****** - Verified Buyer
4.5
Purchased this for the X on my E3V2 along with their conversion kit (which is great). Out of the packaging they would hardly move. Stripped them down, soaked everything in 50% Iso Alcohol for a couple hours, dried them, and lubed with Bones Speedcream (as a temporary measure to see how smooth they are, will be changing to a proper lithium or silicon soon). Freshly cleaned and lubed, they still feel a bit grainy on either side, but they move effortlessly and with just a bit of tilt, gravity pulls them all the way.They DO come with 2 rubber endstops preinstalled. The unit is shipped in a thick, sealed plastic bag and heavily coated in shipping grease (not usable for actual lubrication, meant to protect the parts until use).Machining on the ball bearing channel inside the sled looked a bit rough, as does the coating on the rail. Ball bearings look decent, but might be under spec (see below for more info on this).Here's the kicker: I also purchased these (https://amzn.to/3XeZH5E) ceramic bearings to replace them, as they are commonly purchased together (according to amazon) and those bearings have good reviews. I assembled everything and left a 3 bearing space on either side. It was practically locked into place. The tolerances were so tight that I had to use significant force to move the sled. I tried to break them in a bit by manually moving the sled back and forth for an hour, and while that did make things a bit better, it was still entirely too tight to install and move with the stepper. I have a pair of digital calipers coming tomorrow to measure the upgraded bearings and see if they are within spec, but my guess is the coating on these rails have poor QC and due to this they are using slightly undersized bearings to compensate (which also happens to mask the poor machining in the sled). I could tell visually that these bearings were smaller than the ones I purchased, which is why I believe it is the rail and not the bearing upgrades. With the factory bearings though, the item is totally functional and definitely still better than rollers if you don't mind the sound of a cheap rail.I will update my review if it turns out the bearings I purchased were oversized. As of now it is getting a 3.5/5 because while it works, it's definitely not perfect and it took a bit of work to get them there. Will get a 4 if it turns out the bearings are in spec and the ceramics will get a bad review.UPDATE 1/7/23:Measured the upgrade bearings I purchased, out of 30 measured, 29 of them measured within .002mm, most of them being slightly undersized at 2.379mm. This concludes that the bearings used in this rail are terribly undersized, and using any decent in spec bearing will likely lock up your rails. Buy at your own risk. Still a decent value once cleaned and lubed, but not to spec so not worth it long term.
