Lacey and RB Mandy had a 'collar' incident once. Luckily hubby and I got them free fast enough. Layla will chew and/or pull on Laceys collar. I bought Lacey a collar, I'm not sure what you call it, but it can be unsnapped without having to pull on it to get any prong through a hole to get it off. That, along with teaching Layla not to chew on Laceys collar makes me feel better. Also, my dogs don't play unattended.

*edited to add* looked it up in Foster and Smith ,it's called a quick release buckle.