Suitable for 20mm series T slot european aluminum extrusion, Use to build CNC routers, 3D printers, CNC laser cutters, CNC plasma cutters, robotics projects, 3D carvers, machine guards, workstations, etc. 2020 Series T-Nuts carbon steel nickel-plated half round roll in sliding T slot nuts. Made from high quality alloy steel with nickel-plated for good rust resistance and better performance, high hardness and a long service life.