The small collar adjusts between 11.5" length and 16" length. The large collar adjusts between 15.5" to 24" in length. The best way to choose the correct size for your dog is to measure the circumference of his/her neck in inches with a measuring tape and then choose the size that the measurement fits in.
The foundation of these collars is a highly durable, 3/4" webbing for the small collars and 1" webbing for the large collars. The leather we selected is a 6/7 ounce Latigo leather, which will withstand wet/outdoor conditions and is flexible. The buckles, D-rings, and rivets are all made of solid brass to resist corrosion. No plastic "hardware".