The B2G S3 is the very slightly deeper version of the B2 S3, which was our main 1-1/4C equivalent size for many years. This mouthpiece will feel comparable to the size of a 1-1/4C, with just a tiny bit of extra depth, providing additional warmth/richness/darkness of sound. 
 
Prana internal configuration.
 
STC-1 body design.