Knob for use with 3/8" diameter 9/16" hex head bolt. I also uploaded the fusion 360 file so it may be easier to modify to your needs. I am using this to fix a missing knob on my Bowflex power pro where it holds the bench down. New to 3d modeling so its a little crude. You could probable use some glue to keep the knob from falling while screwing in, I opted to just start the threads by hand then lift the nob while I threaded it in.