The 14mm mouthpiece is an appropriate thickness for most horses, according to studies, the average horse only has room for 14mm comfortably, while a thinner bit can place too much pressure in a very small area thus being too strong.
The Kimberly Dee ring allows for lateral steering and turning with a direct feel on the horse’s face to make a more clear aid.
Suitable when a full cheek isn’t appropriate or the look of the Dee is preferred.