The Australian rock star, Ruby, sports the Purple Rain martingale. Martingales are traditionally worn by sighthounds whose heads are smaller than their necks. The function of the martingale collar keeps the collar snug to prevent slipping off the dog's head. But any breed can rock a martingale! Just be sure to get it large enough to slip over the dog's head (or order a martingale with the quick release hardware to easy snap them on and off without slipping over the head). Thanks, Ruby. You're adorable!