What is the infinite battery? Do these Headphones/Earphones really never go dead? As a duo they never do! Just like Batman and Robin when one is fighting the other is charging. This means you always have your Plugfones available and ready to go. Interchangeable pairing means that you just swap the red pair out when the black needs to charge. Amazingly you still get at least 6 hours per set so don't wake up Robin because Batman is still in the fight. At Plugfones we know the battery is king for your work day so we made the duo to keep you rolling no matter how long your shift is or how far you are running. Don't forget Plugfones are the only patented Bluetooth hearing protection. This is not electronic noise cancelation, this is literally an ANSI-rated earplug to block harmful noise. Did we mention how comfortable these are? We have to use earplug-grade foam or silicone to give you hearing protection, but this translates into the most comfortable earbud experience there is. No hard plastic stuck in your ear that starts to hurt after a while. Plugfones also stay put because the earplug creates a seal in your ear. No more earbuds falling out! Premium audio without the price tag! Plugfones are half the cost of other premium brands and with the Sovereign Duo, they are even less than that per set. But just because they are less money doesn't mean we don't dial in our tuned speakers to give you a premium sound experience. Just hook these up to any Bluetooth-enabled device and you are off to the races. The best Headphones/Earphones around.