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 code 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"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: YesFive Step Modes: Full, 1/2, 1/4, 1/8 and 1/16Mix 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: WhitePackage Includes:1 x V3 Extension Board4 x Drivers4 x Heat Sinks.