Cobra"s MR F300 BT is the loudest and clearest way to make and receive cell phone calls on your boat Do you ever worry about getting your cell phone wet or missing a phone call Do you have a difficult time making clear calls while underway or in windy conditions Cobra"s MR F300 BT solves all of these problems.CBRMRF300BT. MRF300BT. Cobra Electronics Cobra Electronics COBRA MRF300 BT Waterproof Handset with Bluetooth Wireless Technology.