I bought a martingale collar today because I've had about enough of Finn's constant pulling on walks (especially now that he's 9 months, 36 lbs and pulls me around) and I used it a few times and I think I'm ready to return it. Many people recommended the collar for pullers but it had zero effect on Finnigan. He'd sooner pass out from lack of oxygen than stop pulling. The snapping sound of the chain doesn't phase him either which is part of the reason trainers recommend the martingale. I think the next thing to try would be one of the head harnesses (Halti or Gentle Leader). I didn't want to have to use one but nothing else has worked so far and he's so strong the pulling just has to stop!