The 7 Shank has quite a bit of weight behind the mouthpiece, which allows a quick release from the rider’s hands.  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" Port: 1 1/2"