We usually have the nylon collars with metal buckles. (Something we learned at our vet's office--If a nylon collar gets dirty and yucky-looking, you can wash it in the washing machine. When Oscar had to spend the night at the vet's and we went to pick him up the next morning, the kennel worker started to put his collar back on. We said, "That's not our collar." Then she told us that she had washed it with some of the blankets and stuff. It looked like new.)

When we had RB Gus, we had to use leather collars because he was terrible about getting out of the nylon collars and taking off Max's collar, as well.