These are designed for attaching an Arduino Mega 2560 with RAMPS 1.4 to 1515 extrusions. The "Fan" version is for use with an RRD Fan Extender like this one: http://www.ebay.com/itm/Reprap-Ramps1-4-RRD-Fan-Extender-2-PWM-controllable-channels-3D-printer-Mendel-/330949831305 I've used an RRD Fan Extender to allow my Arduino to control the hotend fan and bed cooling fan separately from the PLA cooling fans. I connect the PLA cooling fans to D9, so they can be controlled with M106 Sxxx. Then the hotend cooling fan is controlled with M42 P6 Sxxx, and the bed cooling fan is controlled with M42 P11 Sxxx.