A fourth output is available on some models

Total amp hours out

Remote mount electrical box

you can boost the bass by connecting a subwoofer

The polypropelene woofer and rubber surround construction gives you rich sound and deep bass while the minimalistic flush mount installation maintains the look of your boat

Hubbell HBL61CM03LED 30 Amp Subwoofer Grille A fourth output is availableHubbell Locking Devices, Twist Lock, Marine Grade, Ship to Shore Cableset, 30A 125V, 2 Pole 3 Wire Grounding, L5 30, Yellow, LED IndicatorsModel: HBL61CM03LED Bright, durable, LED (green) indicates "power on" High intensity LED is visible even in bright sunlight Totally molded design for superior waterproofing and durability Specifications Application Ship To Shore Cables Color Yellow Environmental Conditions Indoor and Outdoor Item Type Pre Wired