VEVOR Linear Guide Rail Set, SBR12 1000mm, 2 PCS 39.4 in/1000 mm SBR12 Guide Rails and 4 PCS SBR12UU Slide Blocks, Linear Rails and Bearings Kit for Automated Machines DIY Project CNC Router Machines

Nice rails for the money you can’t beat it, Steve

At first I noticed the rails did not lie not completely flat, deflecting 1-2 mm from center to end. This is because the steel bar and aluminum rail adapt to temperature changes differently, so I loosened the screws attaching the bar to the rail with a 3mm allen wrench, let them sit overnight at room temperature, and tightened them the next day. Problem solved.

Quality item for making a router sled.

I wanted a better, more ridged platform for the Y axis on my CNC machine, this worked great. Yes they are upside-down.

Absolute garbage product. The cubes are not balanced so if you use them as a single track they fall from side to side and get stuck instantly. Impossible to use as a single unit, you have to use two tracks side by side, which for many uses invalidates the use. If the rail was oval instead of perfectly round than it would work as intended but due to the round rail, and poor design of the cube slider, it does not work as intended at all.