The author remixed this model.
I added an extension so the cap/nipple can be removed temporarily and it will hang on there. The hole is 11mm because the brake bleeders screws on my car use a 11mm wrench to loosen and tighten. It needs a hook and pick set to stretch and fit over the nut part of the bleeder screw. Print in TPU hardness of choice. I used 95A and it stretches enough to fit tightly.