M-Series 1-inch Marine Component Tweeters (100 W, 4 Ω) - White Sport Grille. Purpose-engineered and built for real marine duty, the M-Series component speakers deliver maximum audio performance in any open-air boating environment. The M100-CT is a 1-inch, pure silk dome tweeter, specially treated to withstand the marine environment. Silk has been chosen for its lightness, excellent damping properties and smooth response characteristics. You will appreciate the clean, articulate high-frequency response of the M-Series dome tweeter, especially at higher volume levels.