This may be the strongest collar (for dogs) that is on the market today.

This very strong big dog collar has spikes all the way around to protect the dog's neck.  This nylon reinforced guard dog collar has two layers of leather with a piece of nylon webbing between the layers of leather.  The spikes help to prevent an intruder from grabbing the dog's collar to control the dog.  The spikes also guard the dog's neck when play fighting with another dog.  We guarantee this collar for 24 months