This is a very simple Direct-Drive Extruder for 1.75mm Filament optimized for Flexible Filaments and easy Filament change. For a Bowden version see:http://www.thingiverse.com/thing:636178 For a smaller NEMA14 version see: http://www.thingiverse.com/thing:643582 Other required parts: Merlin Hotend: http://reprap.org/wiki/Merlin_Hotend Drive Gear 8mm OD 13mm length: http://reprapteile.de/mechanisch/direct-drive-geraendelter-pulley-drive-gear.html Nema 17 Motor 624 Bearing 2x M3x12 1x M3x25 1x M4x10 1x Spring 7mm OD 30mm length 40x40mm Fan (sleeve bearing recommended) Screws for the fan Update 2015-03-06: Made the fan mount holes go through the block to allow longer screws for more stability