Coaxial Speaker System: 4-inch (100 mm) Woofer, 0.75-inch (19 mm) Silk Dome Tweeter The Evolution C2 systems deliver sparkling high-frequency detail, smooth mid-range and powerful mid-bass, thanks to real silk dome tweeters and precision-engineered woofer designs. The C2-400x system features 4-inch (100 mm) woofers with mineral-filled polypropylene cones, long excursion capabilities and stamped steel frames. The woofer design benefits from JL Audio's vast woofer design experience and advanced modeling systems. Breakaway mounting tabs on the woofer frame allow the C2-400x to be installed in four-hole or two-hole configurations. Injection-Molded adaptor plates are also included to allow mounting of the C2-400x speakers into a 4 x 6 (100 x 150 mm) speaker location. Tweeters are coaxially mounted and built with 0.75-inch silk dome diaphragms that deliver smooth, extended response, on and off axis. The small size of the C2 tweeter minimizes tweeter protrusion, allowing C2 coaxials to fit behind most factory speaker grilles. Speaker grilles are included, each consisting of a black grille tray with satin silver accents and a black steel mesh grille with an electroformed JL Audio logo. Sonic character: Clean and Dynamic Sold as a pair.