Very similar to previous design (https://www.youmagine.com/designs/nema23-direct-drive-extruder)  but after a good number of iterations and tweaks the design is much better now. I have been able to extrude ninjaflex through a bowden tube (as short as possible).  I recently have switched to 4mm compression fittings for bowden tube attachment. This makes dealing with jams or stuck filament much easier and doesn't seem to fail like quick-connect fittings eventually do. There are a variety of motor attachments. I have a custom one for each of my printers (SpiderBot, RoStockMAXX, and RoStockFAZZ) with NPT or M8 fittings for each.