Professional's Choice 7 Shank Collection Slow Twist Wide PortThe 7 Shank has quite a bit of weight behind the mouthpiece, which allows a quick release from the hands of the rider. This is an excellent transition bit out of an O ring or D ring. The square port is more aggressive than the traditional rounded port because you are working off the corners of the mouth. The twisted bar pieces are more aggressive. Mouth: 5 1 8" Cheek: 6 1 2" SKU: PCB 1047