mini sound amplifiers aids | set of 2 with portable charging case upgrade rechargeable stylish 300mah clear sound adjustable volume looks like earbuds 26 sawyer doctor portable charging case - the protection box has built-in 300mah battery, which is convenient for charging the earphone through magnetic contact anytime and anywhere. it can be used for 10-12 hours after charging 2 hours, lasts longer than other types of device.