This product is a 4-digit red color digital tube module It is controlled by I2C. Only 2 IO ports can control the 4-digit nixie tube, which greatly saves the number of IO ports. The control chip is HT16K33 , Strong compatibility, compatible with most microcontrollers. Working voltage: 5V (3.3V is relatively dark) IIC address: default address 0X70 Digital tube size: 0.54 inch