Summary This clamp fits a standard 1/2" pvc pipe and will secure using an M4 16mm long and a nut. Probably a #6 would fit as well, but I haven't tried. As you can see, I'm using them to secure a couple of candelabra bulbs that I had left over from removing those stupid things. I decided they are nice a small and will assist me in heating my box to cover my 3D printer. :D Use them to secure whatever you have a small bracket for, or take to TinkerCAD and add too it to suit your need. Enjoy.