Plantronics mobileheadset amplifier3 times louder (up to 24 dB)Easily connects between phone and headsetHeadset not includedVoice/sound activated operationAutomatically turns on/off to conserve batteriesBelt clip includedLightweightRequires 3 AC675 standard hearing aid batteries (included)Works with most cellular and cordless phones with a 2.5mm jackAlso works withcorded BTS phones with a 2.5mm jackDimensions: 2" x 1.5" x .5"Dark grayREPLACEMENT BATTERY: BATT-HA675E-4PK (4 pack)PLMHA100