This is a 1/4 20 UNC thread bolt kit & nut The nut is a fixed size with a 10mm hex (across the flats) (& yes I know I am talking metric on am imperial thread, get over it). The bolt kit consists of: 10mm hex bolt top. 20mm length 1/4 20 thread. 40mm length with a 1/4 20 thread (shank is 6mm). 50 mm x 6mm OD shank (you can use this with the 1/4 20 thread already above, just set the shank to the length you need. Use the HOLE function to create a thread in anything you need.