Review on Adjustable Depth 1U 19 inch Server Rack Rails by StarTech.com - Universal 4 Post Rack Mount Rails Kit for Network Equipment, Servers, and UPS - Compatible with HPE ProLiant and Dell PowerEdge (UNIRAILS1UB) by Brian Page

I have an old 440mm wide 3U Supermicro case that can weigh between 100 and 140 pounds fully loaded and NONE of the mounting solutions will fit in the old server rack that I'm using. FINALLY this 1U 200lb rail kit fits. The rails are a little thicker. They claim to be universally compatible, but my 440mm wide case fits SIMPLY perfectly (after loosening, adjusting and re-tightening the screws to ensure make sure they sit snugly on the rack). If the case was just a few millimeters wider I doubt it would fit. If you need this for a device that's close to the sides I would measure to be sure ensure that it fits. (At the same time, I have a 4U ATX case that fits quite loosely, so your mileage may vary.) Overall, I'm very happy with them. I'm ordering a second set and may get a third soon.