This is the smaller of our two corrections. It is both narrower and shorter than the TM 22. I find this bit to be really good for a horse that wants to over bridal. The reason it’s good for that is because it has much less tinge relief than most port bits; so when the horse over bridals and rolls their head down to the spot where they would normally escape from the pressure of a standard port, the TM 21 continues to engage in their tongue making them pick their head back up. There is a significant element of horsemanship in the scenario I just laid out. The rider must know when to keep the pressure applied and when to give the release when the horse’s head comes back up.