The SEAUSBMINI-P is an adapter that allows a stereo's rear RCA input and rear USB input to be accessed on the helm. To describe further, a marine stereo is engineered with all inputs and outputs on the backside of the stereo. This is done so that the front of the stereo (faceplate) is waterproof. However, this means that these valuable connections need to be accessible and hence the need for a SEAUSBMINI-P. Simply plug the connections of the SEAUSBMINI-P into the rear stereo inputs, cut out a 1 3/8" hole, and install the adapter with the accompanying rear nuts.
Please note that the SEAUSBMINI-P only has 5" of cabling so make sure you install this adapter close to your stereo!!