Features: The RAMPS 1.4 board is designed to fit the entire electronics needed for a RepRap in one small package for low cost. RAMPS interfaces an Mega with the powerful MEGA platform and has plenty room for expansion. The modular design includes plug in stepper drivers and extruder control electronics on an MEGA shield for easy service, part replacement, upgrade-ability and expansion. Additionally, a number of expansion boards can be added to the system as long as the main RAMPS board is kept to the top of the stack. Mega is a micro-controller development board itself has 54 groups digital I / O input / output terminal (14 groups do PWM outputs), 16 sets of simulation than the input side, group 4 UARTs (hardware serial ports), using the 16 MHz crystal oscillator. With the boot-loader, download the program directly via USB without having to go through other external writer. Supply part of the optional USB power, or as an external power using the AC-to-DC adapter and battery. Development IDE interface is based on open-source principles, allows you to free download for use in project work, school teaching, motor control, interactive works. A4988 driver is a carrier board or breakout board for Allegro's A4988 DMOS micro-stepping driver with translator and Over current Protection by Pololu; This stepper motor driver lets you control one bipolar stepper motor at up to 2 A output current per coil. Specifications: RAMPS 1.4 Size: 9.1 x 5.9cm / 3.58 x 2.32" Board for R3 Size: 10.8 x 5.5cm / 4.25 x 2.16" A4988 Color: Green A4988 Quantity: 5pcs Package Includes: 1 x RAMPS 1.4 Board 1 x Board for R3 5 x Soldered A4988 Drivers 5 x Heat Sinks 1 x USB Cable 15 x Jumpers .