The second-generation JBL Micro II is the first ultra-portable speaker that has a Li-ion (lithium-ion) rechargeable battery and a built-in bass port. With a 1-5/8-inch (40mm) driver and an acoustic volume of 100cc, the JBL Micro II delivers legendary JBL sound with exceptional bass -all in a speaker that fits easily in backpacks or clips onto clothing. A built-in audio cable connects to any mobile device or MP3 player, and it can even be daisy-chained with other JBL Micro II speakers for a powerful sonic experience.