Up to 85% efficiency thanks to ADC (Advanced D-Class) output stage ^^ USS (Universal Speakers Simulators) allows SP 4.900 to work with head units featuring the speaker load detection circuit ^^ 160 x 4 RMS (4) with ultra-compact size ( 211.6 x 130 mm) ^^ IP55 aluminum chassis for maximum protection against humidity and external agents ^^ Water Jet Resistant