A loose ring bit with a chain-style mouthpiece for greater control.
A Waterford bit has a chain-type mouthpiece with ball-shaped links joined together. It discourages fixing, blocking, and leaning on the bit. Add bit guards (item # 13740 or 13741) if you are concerned the corners might pinch.
Always wash a bit after each ride. Remove from bridle and soak in hot water. Use small brush to remove residue. Dry with clean towel.