This product is discontinued, please consider the Raspberry Pi RTC Expansion Module v1.1 as an alternative. This is a Super Capacitor Real-Time Clock module, it design for Raspberry Pi, but it also can be used to Arduino. Pluging it into Raspberry Pi GPIO interface, and all is ok. This is the easiest way to keep it in time. Compared with the Mini RTC Module，it not include battery. Because it has super capacitor.Features: Super capacitorSmallerWork in 3.3V and 5VSupported Raspberry Pi and ArduinoCompatible with Raspberry Pi A+,B,B+/2.Specification: DS3231 RTC ICSelf-adjust 3.3V and 5VSize: 14x16x12 mm