"Air bypass valve virtually eliminates the chance of hydro-lock in the event the filter of your AEM
Cold Air induction system becomes submerged in water. The valve installs along the upper portion of the inlet pipe and shuts down induction at the filter when it becomes submerged, rerouting air through its external diaphragm to keep water out and air flowing in."
A money making scheme. Your only every going to need one if you drive through lakes!!
I suggest that you get the AEM CAI
. I love mine.