Upgrades all David Clark H-10 series headsets (& clones having domed ear cups) to active noise reduction technology. This kit uses 2 pre-assembled ANR modules that replaces the original headset speakers. Other kit components include a 9V battery pack, cabling, installation materials & instructions. (Std 6′ cabling tie-wraps onto existing audio cable & requires a 1/4″ hole in left ear cup; optional AMP cable available) Installation time: 1-2 hrs. Noise reduction: 18-21 db @ 200-300 Hz.