150mm MGN9 Linear Rail Guide with MGN9C Carriage Block for 3D Printer and CNC Machine

Cheap, yet actually smooth! They say they that chinese rails are always sticky and/or rough, stuffed with thick factory grease. These appear to be an exception. It arrived sealed in a sealed package with a light oil, and came with a ziplock bag with a few extra bearings (which appear to be slightly larger than standard chinese mgn9 bearings, which I take as a sign of quality, but be aware). They run pretty smooth and will slide down the rail by themselves (as opposed to some other cheap rails...). Overall, if you're looking for functional, yet cheap linear guides, these are them.

The rails come packaged well with a light oil film, not the thick glue/grease like other brands. They don't require any cleaning to move smoothly - Although I did add a light grease.The best thing is that I didn't have to wait 3 weeks for shipping.However, one of the rails was bowed up by about 10mm/m (when sitting on a flat surface). This would probably resolve itself and be fine if you are bolting it to a decently rigid structure. Luckily I ordered extra rails.All 4 of the rails were straight along the sides, except for the bow mentioned above.

Used for the v0 mgn9 mod and it got rid of the wobble completely, great rail

I used it to upgrade my laser cutter.The rail fits good and moves very smoothly.It came preoiled.

I bought one of these to convert my printer's x-axis and it was relatively smooth out of the box. Took it apart, cleaned everything with isopropyl alcohol and relubed with krytox and it was amazingly smooth. I then decided to buy another one to upgrade another printer and it the quality was dramatically worse. The second one could not move without force. There was a lot of binding and grinding. I was going to give it a clean but upon checking the rail, there was about 1mm deflection in the middle. This probably the reason for the binding. 1mm in the middle of a 350mm rail is really bad. I will be returning the second one.

Nice rail

Used as an x axis upgrade on my 3D printer. Worked perfectly, very smooth and great for the price.

When I received the rail, the carriage block would move smoothly in one direction, but not the other.Turned out it was bent enough that, when I laid it down on the table, I could push on one end of it and the entire rail would go up like a seesaw.Didn't need it for a while, so I tried to bent it back by hand, but it snapped in half.This things are brittle as heck, and that failure means it wasn't shipping damage.The rail was that bent from the factory and they sent it out anyway.You might get lucky with the rail you buy, I certainly have in the past.It's just good to know you don't always get lucky with the cheap rails.