a “limited slip collar”, a martingale is a 2 part collar. The bottom is a
larger loop and the top is a loop that the bottom chain slides on to open and
close. Unlike a choke collar, a martingale will only close to its limit; not keep
getting tighter like a choke collar. Size of the collar is determined by the
large lower loop. You want the collar to
fit high up on the dog’s neck without the rings touching at its tightest point
but still go over the dog’s head. To determine the size needed, you need to
measure the dog’s head at its largest point.