This D ring is made from 5/16" diameter material and has an outer diameter of 2 7/8". This D ring is slightly more compact than a normal 3 1/2" D ring. The 5/16" material adds a little more weight which helps the stability and release. The mouthpiece is made of ½” sweet iron and has three equal breaks. This allows for tongue relief, while intensifying the pressure on the outside of the bars.