JL Audio M6-8IB-S-GwGw-4 - subwoofer (200 mm).

M6 8-inch Marine Subwoofer Driver for Infinite-Baffle Use (200 W, 4 Ω) - Gloss White Trim Ring, Gloss White Sport Grille With appropriate system setup, the addition of a subwoofer allows your smaller main speakers to be free of the burden of reproducing low frequencies.
This allows your whole system to play louder and to sound cleaner at all listening levels. Purpose-engineered and built for real marine duty, the M6 infinite-baffle woofers are designed to operate without a dedicated enclosure.
Long excursion capability and rugged suspension systems help produce deep, powerful bass response that will transform your boat's audio system.

The M6-8IB is best used with amplifier power in the 50W - 200W range and is optimized to operate with a large volume of air behind it (at least 1.5 cu. ft. / 42.5 l).
If you prefer to use a dedicated enclosure, refer to one of the suggested designs located in the Specifications section for optimum performance.