The Weymouth works on several parts of a horse’s head and mouth. The shanks add leverage, and place pressure on the poll via the poll strap of the bridle and to the chin groove via the curb chain. The Weymouth F55 and F75 are made with a flat surface, fixed to the mouthpiece, allowing for a snug fit that is stable and encourages precision flexion.
The Happy Tongue Straight is a solid mouth bit which is ported to relieve tongue pressure but is not curved. This makes it slightly harsher than the curved Happy Tongue. The swivel mouthpiece can rotate on the horizontal, allowing the cheek piece to move independently, thereby the horse can set where it finds the mouthpiece most comfortable… removing tongue pressure.