The Minimum Printhead is a drop-in* upgrade for the stock UM printhead assembly. It: *Designed for use with Reptar XY blocks.(http://www.thingiverse.com/thing:154859) Might collide with stock XY blocks... but you shouldn't still be using those anyway! 2013.11.10 - Update: Discovered that running the fan wire directly alongside the unshielded portion of the thermocouple wire can cause unstable temperature readings due to EMI. Keep the fan wire outside the spiral bundle for the several inches between the hotend and thermocouple PCB to avoid this. General Update: When printing without the fan turned on, enough heat radiates from the print into the printhead that this part can soften if it is PLA. Nothing terrible happens, but the hotend will start to slump slightly, so if you print without the fan, it is probably best to print this in ABS or another material. On my other machine, which always uses the fan, I have 100+ hours of print time since installing it... and it is still looking great. 2013.09.23 - v0.8 Changelog: Fixed the M3 hole sizes, which were tighter than they should have been. Tweaked the profile of the bowden-viewing window.