MGN12H 300mm Premium Linear Rail Guide 2 Carriages MGN12 Linear Slide 8mm for 3D Printer and CNC Machine Upgrade

Buying inexpensive linear rails is a total hit or miss. Hiwin is the way to go, but man they're pricy. I really wanted black rails as well, so I figured I'd give these a shot.Ordered two - packaging was meh, they were of course covered in oil to prevent corrosion, but overall the rails moved pretty well. Both rails arrived straight and true, and there's no play in the carriage which is nice too. Properly cleaning and lubricating these made a world of difference, as expected, and so far they've been on my Ender 3 v2 with great success. One had some very minor rough spots that have seem to smooth out without introducing any play, which is always worrying but nonetheless.These aren't the Hiwin rails by any means, but I'm quite delighted with the quality for the price point and plan to buy more in the future. Will definitely update this after I've had some more time with them, but I've had them in use for about 3 weeks now and they've been treating me well.

Purchased for a z conversion on a ender 3. Out of the box the carriage slides great, just cleaned up the rails a little and good to go.

Bought this set and a single rail from another company, this set was perfectly flat and straight, the single rail from another place for the same price as one of these rails, and it was bent like a rainbow! with +1mm bend from one side to the other. These rails are definitely the best bang for your buck!

Make sure to measure your part carefully! The spacing between the main mounting holes is 25mm but the spacing from the end of the rail to the first mounting hole is 12mm, NOT 10mm (DIMENSION E). For the 200mm rail, there are 8 mounting holes total. I modeled this in my design with just the drawing dimensions and had to remake my part due to the bad dimensions. Measure twice, cut once!

this thing rocks, anytime i need SOLID, i mean SOLIDDDDDD linear movement im buying this stuff.literally no play whatsoever even with a couple pounds mounted on it while the track is on its side.

I ordered this item and received one rail and one carriage. The title and image indicate it should have one rail and 2 carriages which is what I needed for my project. Assuming their was some sort of packaging mistake I returned it for another of the same item describing my issue at the time of requesting a return. The replacement I received was exactly the same. One rail and one carriage. I give three stars only because the rail and carriage are great. I have no qualms with the product itself. However, either the product page needs to be updated or whatever logistical error that is resulting in a different quantity needs to be corrected.

These do not operate smoothly. They stick at various places, some of the balls look black and dirty as it moves.. It is supposed to be very smooth and clean in motion. Very disappointed. There are other options (a little more expensive) that are better. Look for the ones that are black and not red and green.

I have bought several brands of inexpensive linear rails. They were all usable but I replaced the bearings in some to get better results. (which may not have been necessary)When I get a new rail, they come with a sticky grease on them. They block moves but I can't lift one end up and have gravity pull the block to the other end. I work on them until I get the block to move from end to end with nothing but gravity from holding one end higher than the other.Instead of taking this one apart, I wiped off as much grease as I could and then poured isopropyl alcohol over the rail and into the bearing area. I then work it and wipe it until I get as much grease off as possible. Then I use PB Blaster white lithium grease from a spray can to lubricate it. I put it on a rag and then wipe it into the bearing block. I was able to get this rail smooth as butter after doing that a few time and working the rail for several times.Another but possibly unnecessary step is to use 2000 or 3000 grit sandpaper to polish the actual rail. The four sides are easy to polish but the little channel is a bit of a challenge. I do that and on some rails that makes a bit difference. This rail didn't have any noticeable burrs but I did it anyway.I was thrilled that it is just long enough for the Z axis of my Biqu B1 SE Plus. I need one more and a conversion kit to install it. I have printers with no v slot rollers (all linear rails) They are nice because there is no adjustment, cleaning or roller replacement needed. They are also very accurate and it seems like I can get a little more speed out of the printer when it is all linear rails.The weight of the Y axis seems to be a little less important and causes a little less ringing with linear rails. (linear advance is the most impactful thing you can do to reduce ringing)Now to find a conversion kit for the Biqu. It isn't like Ender 3 where kits are everywhere. There are a bunch of printable kits though so I may start with one of those.