Fully Programmable Bluetooth® technology, to be used with PDAs, cell phones, computers and other media devices that are Bluetooth® enabled. Sidetone feature, exclusive to SED®. 10 hour rechargeable battery. Automatic voice activation. Speaker volume control. SED® lightweight noise attenuating earcups provide consistent, comfortable protection and superior sound quality. Unique combination of an adjustable behind-the-head steel tension band and two fully adjustable velcro straps provide day long wearing comfort and a secure fit even under a hardhat or helmet.