Turtle Tactio with FlexSpecifically engineered to accommodate the larger or sensitive tongue. Often negates the need to shut the mouth.FlexT UniversalThe Universal cheek provides a number of rein options including the option of a curb strap. But whatever option you choose, the flattened underside of the cannons with their anatomy-inspired recesses are held parallel to the tongue whatever riding activity you enjoy.XSmall – 108-118mm (4.25″ – 4.6″)Small – 118-128mm (4.6″- 5″)Medium – 128-138mm (5″ – 5.4″)Large – 138-148mm (5.4″ – 5.8″) XLarge – 148-158mm (5.8″ – 6.2″)XXL – 158-168mm (6.2″ – 6.6″)