The Mini Display Kit is based on the DS1307 RTC module and the 0.36” 4-Digit Display module. You can DIY a mini clock after uploading the appropriate code to your Arduino UNO R3. The DS1307 RTC module communicates with the arduino board via I2C interfacde and it can provide year month day of month day of week hour minute second of the real time. There is a CR1220 battery on board so that the IC will continue timing even if the module loses power. The driver chip of the 4-Digit Display is tm1637 and it can be used to display the integer clock stopwatch score and so on. The features are as follows: 1. Compatible with Arduino UNO MEGA2560 Leonardo; 2. 8 adjustable gray of the display; 3. Power supply can be 4.5~5.5VDC 4. Logic level of the interface can be 3.3V / 5V; 5.Each module has 4 screw mounting holes whose diameter is 2.2mm; 6.Nylon screws and nylon hex socket nuts are included in the package so that you can stack the two module together.