SBR12 Linear Rail 500mm SBR12 Linear Rails and Bearings 2Pcs SBR12-500mm Linear Guide Rails with 4Pcs SBR12UU Bearing Blocks, 500mm Linear Rails for CNC DIY 3D Printer Rails

These are great for creating router sleds to flatten wood slabs.

Exactly what I needed!

I hardly ever write reviews- so this is important to me. First the seller was extremely responsive when they bearings did not arrive the the rails. They sent them out right away!Finally, I set these up and neither of the rails are straight. There is a slight bow in both. I mounted them on perfectly flat track. One is off by a hair (except able for what I am doing). But the other is lower in the middle by an 3/32 inch! I don't get it. I measure and check the mountings over and over- FLAT. Then I looked to shim the middle and the gap disappears... but it should be higher at that point, right?I even switched the sides of the rail to confirm is was not the platform itself. I spend a couple hours disassembling and reassembling EVERYTHING trying to trouble shoot. And this is my conclusion.

It works for my needs but honestly i was expecting more precision. The mounting holes on the ends are off by a few mm i dont recall the exact measurements off the top of my head but for example: left side holes where 10mm from the end will the right side is 12mm from the end. Its a pretty negligible difference but it might be important for some one. Also it appears that the blocks that come with each rail are supposed to stay with that rail so dont mix them all up in a pile like i did, i spent an hour trying to find which one goes to each rail. Also some other reviews metioned it but ill say it here to, youll need M5 screws/bolts as for length that just depends on the thickness of material your using. I used m5x25mm for the wood portions on mine and m5x20mm when mounting the rails and blocks.

First off, for all the people thinking are buying super high end precision cnc parts, you are kidding yourself. There is a reason these are a quarter the cost of parts from avid cnc or other reputable brands. These are inexpensive for a reason and should be treated as such. So if you want super high end quality controlled engineered parts, go buy them. Otherwise stop complaining. These rails are good to go for my needs and the bearings are pretty crappy, but for my needs I'll make them work. I also knew what to expect based on the price. If I wanted perfect I would have spent a heck of a lot more than $40-ish.

I think it will work for what I need it for. Seems to be good quality maybe not 100% but will work for me. They did send the wrong bearing blocks so I sent them a message and they corrected that very fast. Will definitely buy from again.

Good quality rails, great customer service! I am going to make a slab flattening router jig with them. they were missing the block sliders due to shipping damage the box was blown out on the end, customer service got me a new pack of 4 slides at no charge.

I needed slightly different lengths. But they were back ordered so I got shorter ones and butted them together, passes over smoothly.