I had a problem with my original tube, it was a slightly small diameter and even the stock Ultimaker PLA wouldn't pass through it.I obtained a new PFA tube and ran into issues getting it to hold it in both ends tight enough (the original bowden tube is slightly larger on the outside). Hoping these instructions save you that grief! :DAs an added bonus the new tube is way less finicky about filament thickness.-=-=-=-Since Makerbot's latest changes I've felt uncomfortable with Thingiverse. I have switched most of my licenses to NC no derivatives. As this is a derivative of two open models I cannot change the license on this, so instead I've decided to remove it from Thingiverse. Send me a message if you are interested in obtaining this STL and I will be happy to send a copy.