G for "Geyer" and S for "Studio" - the GS is for a darker, smoother cup for playing a Geyer-style horn. Plays with a rich sound and less edge than other mouthpieces but without being too large or unwieldy.
The cup is a med/deep with a slight bowl shape. The backbore is designed to open up the low register and give some flexibility to the slurs. Matched with a #16 bore to keep the efficiency to decent levels, though this does require a bit more air than some of the efficiency-focused models. You're here for the sound, not the cutting power (head over to the model G for that).
Defaults in a #16, available as an #19 or #14 special order. These play 1-2 sizes bigger than the bore number suggests; if you're playing a 12 or 14 now the #16 default might be just perfect.
