The Indomitus collar is made from 25mm wide 3mm thick heavy black rubber. With a stainless-steel buckle. The collar has chain section at the front with a stainless-steel O-ring

The collar has two version:

Version A: Has a single chain loop that is shorter and tighter to the neck. 

Version B: Has two chains one long loop that hangs down with the stainless-steel O-ring joined into it. And a second chain to hold the two halves at the fixed length apart when the larger loop is not being pulled