This is a set of 3 lead screws and nuts which would be ideal for your DIY router, lathe, mill or 3D printer. Each screw is 12" long and one end is machined back 1.5" with a 12mm turned area for your bearings and a 10 MM X 1.5 threaded area for securing. The main threads are 16mm ( 5/8) x 1.5 . The nut has the 16 MM x 1.5 threads inside as well as an external threaded part which is 22 mm ( 7/8) x 1.5 mm threads. The nut also has a flange of 34 mm ( 1 5/16) diameter with 4 tapped holes of 5mm X .08. This offers you 2 mounting options- bolting the flange to your part or threading the flange into your part. These are brand new take-offs from Shopmaster Tri-Power machines which were converted to ball screws at the factory, so they are unused.