Long Shanked Myler Combi with a narrow ported Barrel. The narrow port acts on the tongue. Ideal for strong pullers. Combi means a combination of actions. When the rider first takes up the contact the rawhide covered nosepiece comes into play. If the horse ignores this, then the backstrap  will tighten followed by poll pressure. Lastly the bit will have rotated round to the stopper and then finally comes into action. The Short Shank version of this bit is milder. Horses will either go very well in a Combi or they find the nose pressue too much.