I was just going to say this. Dogs with long, thin heads, like greyhounds, shelties, collies, etc. can easily slip out of regular collars. The martingales are a literal life saver for them.Great for dogs who like to "back out" of their collars. Can't tell you how many dogs with collars that are not properly fitted have slipped their collars while waiting to see the vet!
We still have Cameron in one. We use the all nylon one. The metal from the chain marti stained his ruff.