Nylon mouthpiece with brass rings. This bit is not designed to be used for riding, but is very popular for showing horses and ponies in-hand, particularly when brass buckled led-in bridles are used. Mouth Thickness: 15mm Ring Size: 40mm Sizes: Extra Small Pony (9cm), Shetland/Small Pony (10cm), Pony (11.5cm) Cob ( 12.5cm)