West3D Printing MGN12H-1R-300/350/400/450 Linear Rails with Carriages CNA / H Class

Length: 400mm
Class: S Class
Color: Black
Sale price$28.99

Customer Reviews

Based on 11 reviews
Joe Rivera
Dirty and Disapointed.

I bought 2 rails from here hoping if I avoided the amazon cheap ones I would get good ones. I got them. opened one and found it moved and caught and ground quite a bit. I checked the other and it was the same. Frustrated I took them apart soaked them in 90% alcohol and spun the ball-bearing races. for a while to get all the lube and whatever was in them out. I found some small black bits in the tub I used to soak them and when I picked it up with tweezers it made the same grindy noise I was hearing. Now that both are cleaned and lubed again they seem tighter than the one I did buy from Amazon. I had to clean too, and that slides back and forth easier than these two. Not sure which is normal. Keep this in mind when buying these. I bought the H class steel 470mm.

Hello! We are sorry for your experience. These have been well tested and enjoyed by hundreds of our customers. But the experience is certainly going to be different than you'll find from Amazon rails. These are high preload and are meant to be feel tight (that's as designed). To test movement you should place on a flat surface and 'load' them with a few points of force. This will put relief on the bearings and provide smooth travel.

The design choice is intended to combat axial play which is standard occurance over time especially on rails with little to no preload and can impact print quality negatively.

If you're looking for something a little lighter in preload try our Berserker line which is a premium product offering. LDO rails will also offer less preload.

Thanks for your support Joe!

Good Choice

As mentioned these come with some grease on the rail, but better than rust.

The load is as advertised: they are smooth and sturdy. Bonus is that you aren't working with random dealers from Amazon or AliExpress, but people you can work with.


The linear rails were fine and appeared to be machined well. However the greasing was a bit messy. The carriages appear to have a dedicated grease port, yet the grease was injected through a screw hole that I had to clean out. I also had to break these in manually, running them end to end 40 times for good measure and smoothness.


These rails are a result of a collaboration effort with CNA (BOM Sourcing Guide Recommended) and West3D. We went to them and asked them to think of our use case and design their rails specifically for high speed (and high vibration) 3D Printing. This resulted in us selecting a heavier than standard pre-load (a slight reduction in clearance between the rail and the carriage).

We then moved to improve the design aesthetic over what CNA typically ships. This gave us black carriage end caps and added our West3D logo on the carriage in a way that is tasteful and helps break up the traditional matte silver in the carriage block. We also made sure they provided us carriages with grease ports for your added convenience.

Lastly, we said why shouldn't these be stainless steel, I mean that's kind of our thing.

The result are these rails. We went through and tested 10 rails before listing these, all of our tests provided for a stiff (re: pre-load) but wonderfully smooth glide - especially compared to the standard 'kit' grade rails we tested.  

These rails are transitioning between variants - we now offer a Class H high precision rail. This class provides more consistent straightness (0.1mm over 1 meter length) and tighter tolerance of grooves in the rail (.002mm) with more uniformity over the rail.

Note - for a Voron Trident (and other)  users you require rails 50mm larger than you bed size, you will need multiple of these rails (please check your BOM if you're making build to confirm how many mms you need and the correct quantities).

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