DM2521       Aftermarket diaphragm option for RH 1800 series Diaphragm. Original RH diaphragms are no longer available. This diaphragm fits some of the older RH drivers. Take a good look at it and see if it will fit within the bolts. If not, you might need to be creative to get it to work. The voice coil does fit the driver, but if the mounting screws are in the way of the plastic gasket on the diaphragm, you may need to drill out holes.