CNC Shield Board: 1,Latest CNC Shield Version 3.0 for Ardu ino. 2,GRBL 0.9 compatible. (Open source firmware that runs on an U NO for Ardu ino that turns G-code commands into stepper signals) 3,PWM Spindle and direction pins 4,4-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) 5,2 x End stops for each axis (6 in total) 6,Coolant enable 7,Uses removable A4988 or DRV8825 compatible stepper drivers 8,Jumpers to set the Micro-Stepping for the stepper drivers. (Some drivers like the DRV8825 can do up to 1/32 micro-stepping ) 9,Compact design. 10,Stepper Motors can be connected with 4 pin molex connectors or soldered in place. 11,Runs on 12-36V DC. (At the moment only the DRV8825 drivers can handle up to 36V so please consider the operation voltage when powering the board.) 12,Please note that this is an unassembled kit and Basic soldering skills are needed. A4988 Stepper Motor Driver: 1,A4988 Stepper Motor Driver Board is a breakout board for Allegro's A4988 DMOS Micro stepping Driver with Translator and Overcurrent Protection; please read the A4988 datasheet carefully before using this product. Low RDS (On) Output 2,Automatic current decay mode detection / selection 3,Mix with slow current decay modes 4,Synchronous rectification for low power dissipation 5,Internal UVLO 6,Crossover-current protection 7,3.3 and 5 V compatible lo gic supply 8,Thermal shutdown circuitry 9,Ground fault protection 10,Load short-circuit protection 11,Five selectable step modes: full, 1/2, 1/4, 1/8 and 1/16 U NO R3 Board for Ardu ino: MCU: ATmega328 USB interface: ATmega16U2 Operating voltage: 5V Digital I/O pins: 14 (including 6 with PWM capability) Analog input pins: 6 I-I/O pin output current: 40mA max 3.3V output current: 150mA max Flash memory: 32kB (0.5kB used by bootloader- included) Static r am (SRAM): 2kB EEPROM: 1kB Clock speed: 16MHz Package List 4 X 17HS4401S 4 X 4pin cables 1 X cnc shield v3 1 X expansion board R3 with USB cable 4 X A4988 driver