It's designed to be used with the PTFE tubing that comes with the MMU2S and M10 Male Straight Pneumatic PTFE Tube Push for E3D-V6 Fitting Connectors, like these:
https://www.amazon.com/gp/product/B01IB81IHG/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1
The author remixed this model.