Polk Audio CSi3 Center Channel Speaker (Single, Black) A single center channel speaker with butyl rubber surrounds for high performance durability Two 5.25-inch mid-woofers with dynamic balance polymer composite drivers One 1-inch silk composite dome tweeter with a neodymium magnet Acoustically inert, asymmetrically braced 0.75-inch MDF cabinets Power port bass venting for superior clean, low distortion bass