The AP-509 couples the AP-MT4NYL 4" nylon composite mount with the NEW AP-500 Quick Release. Now you can quickly and effortlessly remove expensive electronics from the boat for safe storage. With just a push of the stainless steel plunger pin and a quick twist, your unit is protected. Constructed of corrosion resistant, lightweight and durable materials that will stand up to salt or fresh water environments. Stainless steel mounting hardware included. Not recommended for use with electronics weighing over 5lbs.