Danisgoat: I have been using martindales for a lot of years on Belgians and Westies, in fact since they showed up here in Canada, and never had a dog slip from one. I even showed my Belgians in the show lead version of them. Tinsel came too close for comfort and I can't make it smaller or it won't go over his head as he is deep jawed - I tried. Shocked me when he sat back and it came over one ear. His backskull is really narrow which is why his ears sit so nice and high but his neck is quite a bit bigger where it meets the head. While the effect of the narrow skull, deep jaw and wider neck is pleasing to look at, it makes it difficult to find something that will prevent him from getting loose. So, until he is less inclined to balk he will need a harness or a slip collar. Since it would be too easy to have him self correct - the harness it will be for now.