The fixed rings of a dee ring bit have the shape of a D. A dee ring bit is therefore even more stable in the mouth than an eggbutt snaffle. The D-shape puts more pressure on the horse's cheeks, making it easier to steer your horse.
There are various variants available in different materials. It is important that the version and material of the bit suit your horse. All dee ring bits have an extensive description that helps you choose the right bit for your horse.