SP 4.500 features Hertz ADC (Advanced D-Class) output stage, reaching up to 87% efficiency and delivering an impressive power rating of 90 x 4 (4) W RMS or 300 W x 2 (4) W RMS when bridged, with an ultra-compact size of 192.7 ( 7.58 ) x 130 ( 5.1 ) mm (in. ) x 49 ( 1.9 ). Being ultra-compact with impressive power, SP 4.500 is the ideal choice for Motorcycle applications and for under-seat in sports cars and behind-seat installations in trucks.