1、The expansion board can be used as engraving machine, 3D printer and other drive expansion board. 2、Compatible with GRBL 0.8. Open source firmware running on for that converts G code commands into stepped signals. 3、PWM spindle and direction pins, support 4‑axis (X, Y, Z, A ‑ you can copy X, Y, Z or use the pin of D12 and D13 to custom firmware to perform the complete axis 4). 4、Compact structure, stepper motors can be connected to 4 pin connectors or soldered. 5、This is a set of disassembled parts and you need basic soldering techniques to solder them together. Features: The expansion board can be used as engraving machine, 3D printer and other drive expansion board. Compatible with GRBL 0. 8. Open source firmware running on for that converts G code commands into stepped signals. PWM spindle and direction pins, support 4-axis (X, Y, Z, A - you can copy X, Y, Z or use the pin of D12 and D13 to custom firmware to perform the complete axis 4). Compact structure, stepper motors can be connected to 4 pin connectors or soldered. This is a set of disassembled parts and you need basic soldering techniques to solder them together. Specification: Radiator Size: Approx 8*8mm CNC Expansion Board: Version: V 3.0 Voltage: DC 12V-36V (only DRV8825 driver can handle voltages up to 36V, so please consider the power supply voltage) Board Size: Approx. 68 x 53mm / 2.7 x 2.1in A4988 Driver Module: Thermal Shutdown Circuit: Yes Crossover Current Protection: Yes Ground Fault Protection: Yes Short Circuit Protection: Yes Compatible Logic Voltage: 3.3V, 5V Five Modes: full, 1/2, 1/4, 1/8 and 1/16 Size: Approx. 20 x 15mm / 0.8 x 0.6in Mix use the slow current decay model. Internal UVLO and low RDS (on) output. Current decay mode automatically detected/selected. Three-phase rectification, low power consumption.   Package List: 1 x CNC V3 Expansion Board 3 x A4988 Driver Module 3 x Radiator