Utilizing patented technology for the surround (US Patent #7,275,620) ALDS Technology SPV Technology Spider with interlaced tinsel leads Original MTX steel frame Glass fiber cone Stitched cone to surround Butyl rubber surround High temp (220�) aluminium voice coil Tripple stacked magnets High-end, heavy duty Streetwires terminalsSquare subs have more cone area than round subs and thus give MORE BASS. The T6000 square subs can be used in both sealed and vented enclosures.