Hartman and RoseSizing Guide
Measuring you dog's neck:
Hartman and Rose sizes are measured from the end of the buckle to the first hole and to the last hole. The adjustment from the first hole to the last is 2 inches.There are five holes. To measure for your dog, use a cloth tape measure or a piece of string and measure snugly, but not tightly around your dog's neck. This will be the small length of the collar. This leaves up to 2 inches to lengthen the collar to make it fit comfortably.
If your dog's snug (comfortable) neck measurement was 12", you would pick a collar size of 12" - 14".
If your dog's snug (comfortable) neck measurement was 15.5", you would pick the collar size closest to 15.5". This would be the size 16" - 18" collar.
If your dog's snug (comfortable) neck measurement is exactly in between two sizes, then pick the smaller size.