I bought a small and a medium, though both collars are small. The medium fit easier, but was thinner than the small tag. The small was too small to get over the collar, so I had to take some pliers to open them up and get them on. I would recommend the small due to thickness, but it’s quite a challenge to get them on. Overall, I am pleased with them even though some of the writing came off with the tape. Lol.