Feature: 1. CNC shield uses removable A4988 or DRV8825 compatible stepper drivers; the CNC shield extension board can be used for carving machine, 3D printer driver expansion board. 2. GRBL 0.8 compatible. (Open source firmware that runs on an board that turns G-code commands into stepper signals); PWM Spindle and direction pins,4-Axis support (X, Y, Z , A-Can duplicate X,Y,Z or do a full 4th axis with custom firmware using pins D12 and D13). 3. Small size and compact design, Stepper Motors can be connected with 4 pin molex connectors or soldered in place. 4. A4988 Stepper Motor Driver mixes with slow current decay modes; internal UVLO and low RDS (on) output. 5. Automatic current decay mode detection/selection; synchronous rectification for low power dissipation. Specification: Features: CNC shield uses removable A4988 or DRV8825 compatible stepper drivers; the CNC shield extension board can be used for carving machine, 3D printer driver expansion board. GRBL 0.8 compatible. (Open source firmware that runs on an board that turns G-code commands into stepper signals); PWM Spindle and direction pins,4-Axis support (X, Y, Z , A-Can duplicate X,Y,Z or do a full 4th axis with custom firmware using pins D12 and D13). Small size and compact design, Stepper Motors can be connected with 4 pin molex connectors or soldered in place. A4988 Stepper Motor Driver mixes with slow current decay modes; internal UVLO and low RDS (on) output. Automatic current decay mode detection/selection; synchronous rectification for low power dissipation. Specifications: CNC Shield Board -- Version: 3.0 Color: red Size: 6.8 * 5.3 * 1.8cm / 2.68 * 2.09 * 0.71in VoltageL DC 12-36V (at the moment only the DRV8825 drivers can handle up to 36V so please consider the operation voltage when powering the board.) A4988 Stepper Motor Driver -- Color: red Size: 2 * 1.5 * 1cm / 0.79 * 0.59 * 0.39in Thermal Shutdown Circuitry: yes Crossover Fault conservation: yes Load Short-Circuit conservation: yes Compatible Logic Suppluy: 3.3V and 5V Five Selection Step Modes:full, 1/2, 1/4, 1/8, 1/16 R3 Board-- Color: blue Size: 6.8 * 5.3cm / 2.68 * 2.09in Package Size: 15 * 11 * 4cm / 5.9 * 4.33 * 1.57in Package Weight: 90g / 3.17oz Note: This is an unassembled kit and Basic soldering skills are needed. Connecting or disconnecting a stepper motor while the driver is powered can destroy the driver. Package List: 1 * R3 Board 1 * CNC Shield Board 4 * A4988 Stepper Motor Driver 4 * Heat Sink 1 * USB Cable 1 * 40-Pin Row Needles Package List: 1 * R3 Board 1 * CNC Shield Board 4 * A4988 Stepper Motor Driver 4 * Heat Sink 1 * USB Cable 1 * 40-Pin Row Needles