When the UM3 was released I asked Gudo if he could mod a couple cores to 1.75mm, that's how this design started. We had the idea of creating a Flexible Fixed Point to have a slightly more rigid Core to improve the print quality and also to swap nozzles faster without damaging the thin Heat Break of the Core while doing so. In the spirit of Open Source Gudo and I would like to share the Step files of the modded parts, this will help future modders to keep developing around the Core concept. Of course remember all this changes if done are at YOUR OWN RISK of DAMAGING A CORE, and should not be done without much know-how. Also all the files where made from a real Core, NO UM FILES WHERE USED TO MAKE THIS. This design should only be used for non-profit developments. More information about why & other mods done to the Printhead at: http://www.3dprintingforum.us/viewtopic.php?f=57&t=521&start=15