SOLD AS A PAIR, Many Frequencies Available - Contact us if you need help selecting the proper frequency. The Harrison Labs FMOD is an in-line active crossover simulator. FMODs are passive so noise free & better than a much more expensive electronic crossover that requires power to operate. Frequencies available for every need such as: Subsonic filter, Subwoofer, Woofer, Midbass, Midrange, Tweeter, Super Tweeter, Horns and Ultrasonic filter Combine with other FMODs & traditional electronic crossovers for bandpass ranges or to change the slope and crossover frequency point Install in seconds by placing the FMOD in-line with the RCA patch cable running between the source (head unit/preamp/etc) and the amplifier Low Pass available Frequencies: 50, 70, 100, 150, 200, 500, 1000, 2500, 3500, 6500, 20K High Pass Available Frequencies: 20, 30, 50, 70, 100, 150, 200, 300, 500, 1000, 2500, 3500, 6500