Longruner GRBL CNC Shield Expansion Board V3.0 +UNO R3 Board + A4988 Stepper Motor Driver with Heatsink for Arduino Kits (Arduino Kits) Latest CNC Shield Version 3.0 for Arduino. Arduino UNO R3 Board, MCU: ATmega328, USB interface: ATmega16U2. PWM Spindle and direction pins. 4-Axis support. Runs on 12-36V DC. 2 x End stops for each axis (6 in total). 4Pcs A4988 Stepper Motor Driver with radiator.