This O-ring is made out of 5/16" diameter material. 2 7/8" outside diameter against the extra weight in the compactness of the ring allows for a more stable feel and quick release. The mouthpiece is made of  1/2 " sweet iron and has three equal breaks. This allows for tongue relief, while intensifying the pressure on the outside of the bars.

Mouth: 5  1/4 " Rings: 2  1/2 "