The Sport-tac ear defenders specifically designed for hunters and marksmen, the slim profile avoids contact with the stock. These collapsable earmuffs also feature a smooth active volume function to eliminate abrupt sound cut-off. Audio input for external radio. Additional high visability outer shells. Low battery levels indicated 10 hours before they run out. New ASIC Technology for lightning fast response to Impulse Noise Amplifies ambient sound Audio Jack for cell phones/mp3 player,radio etc Auto shutoff 500 hrs battery life. Interchangeable Green/Orange Cup Inserts Hygiene kits can be purchased for this item.