RTCSD-01 - REAL-TIME CLOCK AND MICROSD BREAKOUT 3.3-5VThe Realtime clock & microSD breakout keeps accurate time and supports external memory through a microSD. The breakout features the DS1307 Realtime clock with battery holder for reliable time readings in case of breakout power outage. The RTC SD Breakout also features a microSD card slot adding external memory to read write pictures text files audio and much more. Add accurate time measurement and external memory to your next Arduino project! 100%