This RAMPS is pre-assembled.
Here are some items needed to complete your 3D printer electronics:
1x Arduino Mega 2560/1280
3x Mechanical or Optical Endstops
4x Pololu Stepper Drivers w/ heatsinks
1x USB 2.0 Cable
1x Min 12V 5A DC power supply required (up to 16A total required if heatbed is used)
4x or 5x Motors