30L/50 is based off the orginal Geib profile made wider in the inside diameter (1.295). The cup is more bowl shaped than the  standard 30L with a little more depth.

See the 30L description below.....

Similar to the Geib but with a more open entrance to the throat. It is a flatter rim with a .323 throat and our standard backbore. This mouthpiece is extremely versatile throughout the range of the horn and produces a even, dark sound.