I printed a similar model and assumed it would fit the AMS dry box. It did not, and the maker did not include the funnel dimensions. I drew this one up in Fusion, and it fits the box perfectly. The outside dimension of the small end is 15 x41 mm (about 9/16 x 1-5/8 inches). The large end measures 45 x 75 mm (about 2-15/16 x1 13/16).
The author marked this model as their own original creation.