Versatility and quality define the Polk Audio MM651 speakers. Due to the fact that they are also made for marine use, they feature a Type Dynamic Balance weather resistant dome made from silk composite. These speakers are much like their previous MM series speakers with minute neodymium magnets, which result in a smaller lighter speaker for even more versatility in applications. They are 6.5 inches and also utilize the same honeycomb glass fiber for the woofer cones to deliver clear, clean sounds. If you are seeking the MM651 two-way speaker for marine use, the Kippel optimization in these speakers and their 100 watts RMS promise to still maintain good quality sound when faced with the challenges of various temperature ranges, high humidity, and an open acoustic environment.