Features: Use removable A4988 or DRV8825 compatible stepping driver. The extension board can be used for engraving machine or 3D printer driver. Compatible with GRBL 0.8. Open-source firmware, converting G command into stepping signal. PWM spindle and direction pin, 4 shaft support (X, Y, Z, A - you can copy X, Y, Z or use pin D12 and D13 customize firmware perform complete shaft 4). Compact design, stepping motor can connect 4 pin connectors or be soldered. This is a set of disassembled part, and you need basic soldering skills to solder them together. Specifications: CNC Expansion Board:Version: V3.0Color: RedSize: 68 x 53 x 18mm / 2.67 x 2.08 x 0.7" Voltage: DC 12V to 36V (only DRV8825 driver can handle up to 36V, so please consider voltage for power supply) 4pcs A4988 Driver:Color: RedSize: 20 x 15mm / 0.78 x 0.59"Thermal Shutdown Circuit: YesCross Current Protection: YesGround Fault Protection: YesShort Circuit Protection: YesCompatible Logic Voltage: 3.3V and 5V Five Step Modes: Full, 1/2, 1/4, 1/8 and 1/16 Mix with slow current attenuation model.Internal UVLO and low RDS (on) output.Automatic current attenuation mode Detection/Select.Phase-in rectifier, low power consumption. Warning: Connecting or disconnecting stepping motor while driver is powered on might damage driver. 4pcs Heat Sinks:Size: 8 x 8mm / 0.31 x 0.31" Color: White Package Includes:1 x V3 Extension Board4 x Drivers4 x Heat Sinks