There is no cup inside, as all the inner wall is streight, to make the mouthpiece full taper, the real funnel type mouthpiece. The inside diameter is about 17.5 mms, the classical dimension. This type of mouthpiece is the continuation of the classical horn mouthpiece.
All mouthpieces are precisely the same, as all is made by computer command machines.
All mouthpieces are inspected by myself personally. It allows the velvet sound, the beautiful natural slurs, gliding from harmonic to harmonic. I recommend it for all horn players. It fits as well for the Viennese Horn as it improves the sound quality on the double horn. It has cured many damaged embouchures because of its less resistance against the tone production, less than other mouthpieces.