Intended to be used with a stainless steel pint cup insert. Hole at bottom is so you can push the insert out, and to prevent the cup from being used without the insert.

Link provided to the specific cup I used.

There is a full version of the cup, and a split version for ease of printing.

(https://www.amazon.ca/gp/product/B07CTHKW7G/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1)