The Rubber Mouth Tom Thumb Pelham from Centaur is for the horse who requires a little extra leverage and features a soft rubber-covered mouthpiece for extra comfort. Because it is a tom thumb the shank is shorter, 4" in length, and this is a single-jointed bit. Pelhams require a curb chain and curb rein to work properly. (curb rein sold separately) Centaur bits are perfectly balanced to protect your horse and your ride.