Designed to mount onto the Aluminum Extruder Upgrade Fan Bracket. This upgrade is for the Plus, LC, Simple, and Jr. Find the Aluminum Extruder Upgrade on Printrbot's website at http://printrbot.com/shop/printrbot-alu-extruder/. A replacement for the folded plastic fan shroud. Used to get a more direct airflow for cooling on parts. Designed By: Tommy BertkenThe Printrbot Printrn