DC Dressage bit from Bombers.

DC Dressage was designed to relieve pressure in the horse's mouth as much as possible, creating safe and gentle communication between horse and rider. The key feature of the cheekpiece is the loose ring, which can also rotate. This reduces pressure on the poll and jaw and is not affected by rein aids. The reins are attached to the large D-ring, which moves independently of the cheekpiece. The mouthpiece is fixed to the cheekpiece, with a solid surface that encourages the horse to take contact with the bit. The cheekpiece

DC Dressage can be combined with many of Bombers' mouthpieces.
Happy Tongue Straight is a solid mouthpiece designed to relieve the tongue, but it is not curved. This makes it somewhat firmer than the curved Happy Tongue. Swivel allows the mouthpiece to naturally follow the horse's movements and sit comfortably in the mouth.