This Is A Brand New Compatible Aftermarket Replacement Diaphragm For P Audio Turbosound SD-990 Diaphragm SD990N.8RD Please Look And Make Sure The Diaphragm You Are Ordering Matches The Pictures Above & The Specs Below Specs: Overall Diameter: 4.1" (104 mm) Voice Coil Diameter: 2.8" (72.2 mm) Diaphragm Material: Titanium Nominal Impedance: 8 ohms