These M5 square nuts are designed to work with 20mm V-slot aluminum extrusions, such as those from OpenBuilds, Misumi, or MakerTechStore. They can be inserted from the end of the rail or dropped into the slot at any point. . They are made of nickel-plated steel and have a M5-0.8 thread. They are ideal for fastening brackets, accessories, or other items to your rails. With this pack of 50 nuts, you will have plenty of spare parts for your projects.