These are 120mm fan mounts for the front of your Replicator 2X for materials like PLA that require an cooling fan. They mount to the hinges for the front door so you can swing them out of the way when not in use.

I recommend picking up one of these fan controllers to help control the speed of your fans.: http://www.amazon.com/Silenx-IXAFCEX-Channel-External-Controlle/dp/B0030EZLSO/ref=sr_1_2?s=pc&ie=UTF8&qid=1397663511&sr=1-2

Enjoy!

I printed at .2mm layers, 2 shells and 10% infill.