Bullseye labels them different , the 372 is actually a t-4 frame S400 72mm , they call there t-6 foot turbo's S400's and everything else S300's , the confusing part is every where else a S472 is a t-4 foot turbo and you spec if you want a T-6 foot or the turbine wheel size is another dead give away . In a true S300 chassis the biggest you can go with out a hybrid is the 66mm , anything above that is a T-4 chassis from BW . Here is the current BW catalog