the way I understand it, it takes, lets say, 100hp or less to cruise. The fins allow the converter to hold to roughly this hp level which makes it drive like a tight stock converter. When flooring it, it will overpower those fins and allow full stall. This is more modern, custom build design - as I understand it. My 2400 B&M in the Demon is ok and slips. I want a PTC 4000 "tight". It will cruise fine, and stall when I want it.