The problem you may run into with a nylon collar is that some ferrets will scratch at it, which pulls the nylon threads and can tighten the collar dangerously. Also, be aware that both nylon and leather can shrink if they get wet, so never leave a wet collar on your pet; it may shrink and choke him as it dries. For either of the collars, you may need to make an extra hole, then trim off the extra length and (for nylon) melt the end together. Be sure to leave enough to go through the little ring after it’s buckled. For the ball chain (the kind made for light-pulls or to lift the stopper in a toilet), just snip it to the proper length.
The collar should be loose enough to go over your ferret’s head easily; if it gets stuck on something, better a lost collar than a choked ferret. We’ve never had any problems with either of our ferrets getting hurt by catching their collars in anything, but we make sure to leave them loose enough that the furry snakes can slip out if they happen to get caught. In fact, the easiest way we’ve found to get the collars on is to fasten them, then shove them over the ferrets’ heads while occupying them with Ferretone.
You can also attach the collar and tag using a neatly trimmed piece of stiff wire. For a nylon or leather collar, you’ll probably want to poke the S-hook directly through the collar and put the bell and tag on the same hook, though, since attaching them to the ring on the collar makes them hang down far enough to drag on the ground.