My dog never took to a halti either, they slide up into their eyes and he hates them. (Yess RATTER I had the right size) Instead i have this.
http://www.blackdogtr...-info.php?pid228.html
When the dog pulls, it tightens over the nose, not around the neck, and slides loose when the dog stops pulling. Dear dog used to pull like a train, unsafe as RATTER says, even though mine is a mere 34kg. You put it on in the house, give treat, remove it, later same day put it on lead to treat jar give treat remove it, dog will soon get used then take dog out, move briskly and praise and treat for good behaviour.
I have suggested these to quite a few people now and all of them have come back and said how good they are...no i dont own the company or even have shares....