I've noticed lately that certain ebay sellers are offering generic square rails and bearing blocks made to Hiwin HGR specs.

They are cheaper (new) than most brand name rails are used which makes them tempting. E.g.

https://www.ebay.com/itm/16487670192...oAAOSwnnlgpu8G

Does anyone here have any insight into how their quality compares to THK HSR rails or Hiwin brand HGR line?

I'm not sure how much extra effort THK would put in on their mix n match line (vs their high pre-load matched sets). So much of their precision seems to depend on how well they are installed but they still charge more than 5x the price...

So are the generic rails are a bargain or is there a trade-off in quality?