This expansion board as a driver expansion board, can be used for engraving machines, 3D printers.It is a total of four slots, can drive four stepper motors A4988.Each stepper motor only needs two IO ports.Introduction to UNO module I/O port matching for Arduino.Features:This expansion board as a driver expansion board , can be used for engraving machines, 3D printers.It is a total of four slots, can drive four A4988 stepper motors. Each stepper motor only needs two IO ports. In other words, six IO ports can be well managed by three stepper motors. Very convenient to use.Introduction to UNO Module I/O Port Mapping for Arduino.Note: When inserting the A4988 module, be careful not to insert the reverse. Stepper motor wiring as follows: 2A, 2B is a group (red, green), 1A, 1B is a group (blue, yellow), if you want to change direction, can be change the position of a group, for example 2A, 2B mutually exchanged.Package Included:1X V3 Engraver 3D Printer New CNC Shield Expansion Board A4988 Driver For Arduino Note: The data are all manual measurement, please allow some 1 - 3cm error, due to the light and display difference, there will be some color difference, depending on the physical object received.