There are some good grinder funnels on thingverse, but i could not find one that fit snugly enough in mine without falling over or getting clogged up. This is made for the PomStream salt/pepper grinder. the neck of the funnel is 21mm ID, and grows to 25mm. The PomStream grinder has a 22mm opening, so the funnel goes in a short distance and holds snugly when pouring salt or pepper in it, so you do not have to hold on to it while filling. It is great not to spill salt/pepper all over the place.
printed with brim at 90mm/s, 20% infill, and .2mm resolution. It could go a lot less.