This is a collar my Labrador wore when he was a puppy. His neck is now over 50cm. * Shortest inner circumference: approx. 32cm * Longest inner circumference: approx. 42cm The 42cm measurement is when using the outermost hole, so I recommend this collar for dogs with a neck circumference up to that size. There are no frays or tears, but the holes have linear marks as I adjusted them to fit his growing neck. It's made of cowhide that's about 5mm thick, so it's unlikely to break unless something extreme happens. Please refer to the images. Thank you.