Die Cast Aluminum Super Tweeter - 4 Ohms Impedance.Die Cast Frame - Ferro Fluid Enhanced Voice Coil.1.5 inches High Temperature Kapton Voice Coil - Sensitivity: 102dB (1w/1m).Neodymium Magnet Structure - Frequency Response: 2.5k-20kHz.200 Watts RMS/400 Watts Rated Power - 4.52 inches Diameter/2.73 inches Mounting Depth The OPTIBT38 is a 400-watt, die-cast aluminum tweeter from Lanzar that really gets the highs rolling. With a frequency range of 2.5 to 20 kHz, you’ll have the top end covered. A 1.5 inches high-temperature Kapton voice coil and Neodymium magnet provide rich, sweet highs completely free of distortion. The die-cast frame ensures the security and longevity of your equipment. 4 ohm impedance.