The rails were covered with metal chips and metal dust. They just needed a good cleaning. The bearings run a little rough and bind in several places. After a few adjustments with the hex head screws everything worked fine. I'm using them for a woodworking tool project, so I don't like the high precision that a CNC machine or printer might require. If I used them on a precision machine I wouldn't be too happy and would return them for a better product. You get what you pay for and I got what I expected so I'm happy.
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