Definitive Technology SR-8040BP (Ea) BiPolar Surround Speaker Bipolar dispersion pattern for totally enveloping surround sound that puts you in the action Matching high quality drivers of that found in main and center Definitive Technolgy speakers for seamless sound staging Two 3-1/2" cast basket patented BDSS drivers and two 1" pure Alluminum dome tweeters Easy wall mounting system included