Ground Zero GZRC 165.3SQGround Zero Radioactive SQ lineup is designed and produced for one goal only. Best possible sound quality in the price class. Designed using Klippel optimization with all drivers. These speakers work exceptionally well in typical OEM locations. Woofer is optimized for door installation. Woofer has aluminium cone and rubber surround. Lower 3 ohm impedanze takes out more power from your amp or head unit than regular 4 ohm. Tweeter has a silk dome.