Remake to fit with Printrbots and Ubis hotends. All Printrbot Jr owners should use the base jrhttp://www.youtube.com/watch?v=Xb7hPECXst4 quick filament changehttp://www.youtube.com/watch?v=V1FkHT_6MmU Update 11/2013: added a baseversion with fanmount. Sometimes the filament got stuck in the lower basetube. With this 60mm fan I had no issues. download the counterclock version if your mk8 gear turns counterclockwise to extrude, otherwise download the clockwise versionJust print and assemble it. Parts you need: 2x M3 x 10 1x M3 x 25 2x hotend screws ( 1" 6-32 original ) maybe M4 works too (M3 is too small ) 1x M4 x 50 or bigger hex screw (best a DIN 931 8.8 ) 1x spring 1x 608 bearing 1x M4 nut some M4 washers 1x 60mm fan if needed If you don't have a DIN 931 8.8 screw file the threads of a M4x60 a bit until the spring can slide smoothly.