The Striper Thump Expansion Module is for use in the Hydrowave system. By simply plugging the card into the expansion port in the bottom of the Hydrowave unit, you will add this additional sound to your Hydrowave's playlist. The "Thump" is a sound that has been used for decades by striper fisherman to activate a striper school and to initiate a feeding response on nearby fish. Now, all the work is done with the Hydrowave and you don't have to put down your fishing pole.