AFI Phase II Drop-In Hidden Boat Horn w Black White Grills The AFI Phase II Drop-In Hidden Boat Horn is a compact marine horn featuring an authentic marine sound. This Marine horn has a simple, drop-in installation and mounts from the outside. Comes with two screw-on grills - black and white. Grills have water resistant liners, which keep water out but allow sound through. Although compact, this horn has a new louder dBA rating of 111 at one meter. Installation 2.75 diameter hole x 1 deep. Feat