Features: Memory card interface works with FAT16 or FAT32 formatted cards. 3.3v level shifter circuitry prevents damage to your memory card. Realtime clock (RTC) keeps the time going. The battery(not included) backup can last for years. Onboard3.3V regulator is both a reliable reference voltage and also reliably runs memory cards that require a lot of power to run. Works for Duemilanove, for Diecimila, for Leonardo or for ADK/Mega or higher. Not support for ADK/Mega R2 or lower. Specifications: Model: XD-204 Size: 7*5.4*2cm/2.8*2.1*0.8in Button Cell Type: CR1220 (Not included) Weight: 22g(approx.) Note: 1, This item does no have a Ard (you need to use shield ), or memory card(not included). 2, You will need some basic soldering skills to put them together, and you can get it finished in 15 minutes. Package Includes: 1 x Data Logging Module (Battery and memory card are NOT included) 1、Memory card interface works with FAT16 or FAT32 formatted cards 2、3.3v level shifter circuitry prevents damage to your memory card 3、Real time clock (RTC) keeps the time going. The battery(not included) backup can last for years 4、Onboard 3.3V regulator is both a reliable reference voltage and also reliably runs memory cards that require a lot of power to run 5、Works for Duemilanove, for Diecimila, for Leonardo or for ADK/Mega R3 or higher. Not support for ADK/Mega R2 or lower