The Mikmar Straight and Straight Slanted mouthpiece is available in two sizes. They are 5.25” and 5.5”. Due to the shape of the mouthpiece and function of the bit the 5.25” fits most horses. There is not a lot of lateral movement and no pinching, so for example, a horse that normally fits in a 5” mouthpiece will use the Mikmar 5.25” mouthpiece. This size fits a wide variety of mouth types from large ponies and Arabians to Warmbloods. The 5.5” fits large Warmbloods, for example, a Draft cross with a wide head, large mouth, and thick lips.