MBQUART ZK1-116 6.5 Inch Coalial Speaker System Composite Surround on tweeter dampens dome and lowers fs resulting in and increased useable frequency response up to 20, 000 Hz. Removable tweeter phase lens to be tuned for on-axis (lens removed) or off-axis (lens in place) applications. Mica-filled polypropylene cone mated to a UV butyl Surround and treated cotton spider for optimum accuarcy