Review on Iverntech 400Mm MGN12 Linear Rail Guide With 2 Black Stainless Steel MGN12H Carriage Blocks For CNC Parts And 3D Printer Upgrades by Joshua Gaines

I've purchased these type rails from several vendors for various projects, and with the two samples so far, they've demonstrated very good tolerances/functionality compared to some. One caution: don't plan ahead/predrill your mounting screw holes. It seems that the pattern is not always standardized from vendor to vendor, and I've even gotten some that the pattern was 90 degrees off from stated literature (from another vendor). You would think that this would be standardized, but that has not been my experience. These appear to be a good value for the price and better than some sources from Walmart.