NAGY'S CUSTOMS Universal 10/12 RNRRThese are a CNC molded universal adapter ring, it will accommodate almost anything from a 10" subwoofer to a JLTW3 12". each scribbled line in the adapter ring represents 1 8" increments. So if you need the opening to be 9 5 8 you would cut to the 5th line to get your mounting diameter hole. These are perfect for the guys who may want to run 10" in their drop rail and opt to switch to a 12" later on without tearing their bags up to replace the adapter