The canny collar has a unique behind the head design, making it easy to fit and simple to use. It is the favoured training head collar for the UK Association of Guide Dogs for the Blind, and used by trainers, training schools , rescue shelters, vets and dog owners alike. Unlike other head collars, it does not yank your dog's head to one side, nor ride up into their eyes. For the correct size, measure the neck where the collar part would sit. [https://www.petstation.com.au/assets/images/Capture.PNG]   Size Measurement 1 23cm - 28cm 2 28cm - 33cm 3 33cm - 38cm 4 38cm - 43cm 5 43cm - 48cm 6 48cm - 53cm 7 53cm - 58cm Colossus 58cm - 69cm