This extruder mod allows you to print with some flexible materials with a Lulzbot Taz 5, Taz 6, or Mini standard extruder (maybe other printers too if they use the same extruder). Just put the part under the idler bearing and through your filament (see attached picture). This part prevents the flexible filament from popping out of the extruder since it is so flexible.
This part also works with the standard extruders of the FlexyDually or Dual Extruder, allowing your FlexyDually to print two different flexible materials or turning your Dual Extruder into a FlexyDually. I attached a few pictures I did with my Dual Extruders and FlexyDually using my mod.
I have tested this mod with the following NinjaTek materials:
Cheetah: This material is very new and is as flexible and strong as SemiFlex. It is better than SemiFlex because it can print much faster and doesn't need glue when printing on a PEI bed. This is the main filament I recommend using with this mod and it works perfect with the standard Lulzbot Cura print profiles for Cheetah: http://ninjatek.com/products/cheetah/
SemiFlex: Superseded by Cheetah, but if you already have some, it works okay with this mod. I recommend printing slower than the SemiFlex Cura print profiles. I have gotten some perfect prints with SemiFlex using this mod, but it is not nearly as consistent as Cheetah.
NinjaFlex: I have done some okay prints using this filament, but nothing that good. You have to print really slow (much slower than default NinjaFlex Cura profiles created by Lulzbot), and it still does not work that well. I don't really recommend using this material with my mod unless you already have some NinjaFlex lying around. You may be able to get some decent prints but no promises. I have heard of some people having success with the mod and NinjaFlex though, so your milage may vary!
Remember to use some PVA based glue stick on your PEI bed if printing with NinjaFlex or SemiFlex because it can stick to the bed too well without the glue and damage the PEI. Also, if you're having trouble extruding try messing with your idler tension.
You can download the Lulzbot made profiles here: https://devel.lulzbot.com/print-profiles/cura/ Make sure to go to your respective printers flexible extruder section to download the profile. Ex for the Mini: https://devel.lulzbot.com/print-profiles/cura/Mini_flexystruder_v2/ Change the nozzle size from 0.6mm to 0.5mm!
Use as smooth of a filament as possible (PLA, n-vent, t-glas), but it doesn't really matter. Break small, built-in, single column support off after printing.