The Nina II is designed for a small to medium sized dog, approximately 20 - 35 lbs. It comes with a slightly different tooling pattern and makes a nice medium weight everyday collar.
The Nina II (Fits 12 1/4"-13 1/2" neck)
Tooled black "English" bridle leather buckle collar with stainless steel spots; 5/8" width; Stainless steel roller buckle and O-ring; Fits 12 1/4"-13 1/2" neck
For sizing, place a flexible tape measure around your dog's neck in the place you would like the collar to rest, and pull it to the appropriate snugness, taking note of the measurement. Be careful to avoid fingers under the measuring tape.
If you have a collar that fits well, you may buckle it on the hole your dog is currently using and take a measurement of the INNER circumference, NOT around the outer perimeter of the collar.