I have run the Airtripper, and the PlanetCNC variant Bowden Drives. They work well, but I wanted a few things:1.) Backside access to the hobb gear teeth for cleaning while filament is loaded, or even during a print.2.) Option to drive off a Nema17, or a Gear-Reduced Nema17 which uses a differnt bolt pattern.3.) Alternative to push lock tube fittings to hold the bowden tube, allowing it to extend beyond the hold point (i.e. pass through hold down). UPDATE: I am no longer using a 8-32 nut, I have instead switched to the standard 4mm nut others have used. It is harder to thread around the 4mm bowden tube, but is less likely the tube will come out.4.) Support the filament as close to the hobb & bearing as possible without interference.Available File Types:Zip - Pack and go of the full Solidworks 2014 AssemblySTL'sStepAside from the printed parts for the Nema17 version you will want:1 lot of 4mm OD, 2MM ID teflon tubeqty:2 - 4mm Hex Nutqty:4 - M3 Flat Washerqty:2 - M3 Oversized Flat Washerqty:2 - M3x10mm Button Head Screwsqty:2 - M3x12mm Socket Head Screwsqty:2 - M3x35mm Socket Head Screwsqty:2 - M3x50mm Socket Head Screwsqty:2 - Springs (I used Mcmaster# 9657K283)qty:1 - 608 skate bearingqty:1 - Ultibots 1.75mm Hobb GearIf you go with the Planetary setup add:qty:2 - M3x10mm Button Head Screwsqty:2 - M3 Hex Nutqty:1 - replace ultibots hobb gear with 8mm ID hobb gear like the Mini hyenas gear from makers tool worksOne note: When you thread the 4mm nut around the 4mm bowden tube it will compress on the ID. Get a small drill bit around 2mm and ream the bowden tube back out in that area..