Coronet Flexi Flat Ring Mullen Mouth Eggbutt Bit A Flexi Mullen mouth bit is a slightly flexible bit made of hard plastic and serves the same purpose as the similar bits made of steel. Flexi bits are more acceptable to the horse than regular bits because they are warmer and have a pleasant feeling. The straight (mullen) bit conforms to many horses" mouths and are highly recommended by many equine dental practitioners. This bit has 2 1/2" rings and a 16mm mouth. Made of high quality Stainless Steel core . Sizes available: 5" and 5 1/2"