This is a file for replacing the mk7 plastic extruder feed housing. This design feature material-guidance up to the metal-rod-to-hot-end and not like the original ones only up to the rotating metal-screwlike-wheel (open below). You can see it on the photos. The newer MK8 have this feature anyway. I milled them out of pom and they worked really good until I replaced them recently with all the mk8 easy spring mechanism improvements. Should work with flex material - because of material-guidance. This is only for documentation, design is from summer 2013. I rather would suggest anybody to get a "MK8 kit" from Makerbot (where even the old and bigger MK7 gear fits; about sizes of gears: http://reprap.org/wiki/Drive-gear) so to have a spring loaded drive that makes it more easy to change filament. In Thingiverse you find also the latest "MK8" remixes with closed bottom for flex-material, and as said even the "old" MK7-diameter gears fit on most of them or after adjusting the geometry. Original MK7 here http://www.thingiverse.com/thing:11734 MK8 here http://www.thingiverse.com/thing:53125For milling in POM. 2-sided job for a 3-axis cnc. Rough with a 3mm-Shaft. (Re-rough/Pre-finish with 3mm-Ballhead.) Finish with 1mm-Ballhead.