On January 8th of this year, Polk introduced an improved version of its db Series automotive and marine aftermarket speakers, previously their best-selling model. Three sizes are now available in the 2007 db Series that weren't previously made available (a 3-1/2 inch diameter coaxial, a 4x6 plate-style speaker, and a 6-1/2 inch Slim Mount coaxial for shallow doors. The db651, db651S and db6501 models for the latter size come with adaptor rings that allow the model to easily fit in cars like Volkswagen, Audis, and BMWs. This new series can withstand sun exposure, and water and salt exposure. Since these speakers are Marine Certified, they can be used in different kinds of boats. Currently, the Polk's 2007 db Series speakers are used in award-winning Nautiques ski and wakeboarding boats. The set consists of six full-range round coaxial models, three oval coaxials, one place style speaker, two component systems, and a single component tweeter. With their improved series and for about $120 per pair, Polk offers unsurpassed performance compared to other systems in the same price range.