The loose ring bevel allows a mild lever action with a snaffle mouth. The snaffle mouth applies pressure to the bars, squeezing the tongue. From a size 5″ upwards the ring size increases to keep the bit in proportion for larger horses. Mouthpiece thickness: 12mm (4″), 14mm (4.5″-6″). Cheek height: 55mm (4?, 4.5″, 5?), 70mm (5.5?).