These Chicago Screws are 1/4" and they have an all brass core meaning the shaft that goes inside your punched hole will not bend on you when tightening. The male part of the core has threads that on it and the female part of the core has receiving threads for a secure tighten when you put them together. They do not just pop together like a rivet. The easiest way to instal them is to use a hole punch or even an awl to make the hole first then insert the Chicago Screw and then tighten with a straight slot screw driver. You can also use a bit of glue on the end of the shaft if you would feel more secure that they will not ever unscrew on your bag.