Terra-Forms rock speakers are specifically designed and constructed of the latest aerospace grade composite materials to be particularly durable in the field. Robust construction materials include PP cones, Butyl rubber surrounds, anodized and Teflon sealed components. Simple in installation, yet tough and long lasting for many years of performance and enjoyment. Terra-Forms� outdoor rock speakers are unique in that they not only blend and beautify any surroundings in which they are placed but also provide many additional benefits in full range sound. Terra-Forms� outdoor rock speakers are the seventh generation in a most successful range of simulated outdoor stone speakers. Terra-Forms may offer you the best performance vs. economy available, in any outdoor rock speakers.