anti-fog earbuds come with a touch panel that lets you know when the earbuds need to be charged. The small circle should be the same shade of blue as the reference bar. The sensor in my package was pink, indicating the earbuds needed charging. Charging consists of putting them in an oven at 300 degrees for 5 minutes to remove moisture. Since they can be recharged 4 times, that means I only have 75% of the expected lifespan. I don't plan to test them until my next dive trip in May. I will post after this trip.