If you work with T slot extrusions,these are a must have.These T slot nuts fits perfect on 3030 extrusion or 3030 rail with lots of different components on your rail. to mount something else. 3030 M8 T Slot Nuts for 3030 aluminum extrusion with 8mm slot, use for T-slot aluminum profile 30x30 series. If you also lost pieces to your printer and need replacement, they fit and secure in rails.Use them to add new brackets to stiffen the frame on your 3D printer (Tevo Tarantula). Spring ball loaded makes these T slot nuts sit and stay where you want them,and don't slide around while your trying to into them.It was so much easier than fiddling with the stock T nuts that refuse to lock in place correctly.You can insert and remove these T slot nuts easily. 3030 Series Aluminum Profile T-Nuts widely Use to build CNC routers, 3D printers, CNC laser-cutters, CNC plasma cutters, robotics projects, 3D carvers, machine guards, workstations,and more. Easy to be roll into T slot of aluminum profile., Weight: 0.71760466281 pounds, Manufacturer: NONDK