This funnel is extremely useful and highly recommended when dispensing flake food with Super Feed\'s aquarium feeder model number ASF-1. It is also used, of course, to direct the food into the aquarium without spills. Normally it is with the large end about 1/2 inch into the water. It is made of practically indestructible polypropylene plastic and comes with a retaining plate.
Examples of installation: http://www.super-feed.com/trap.html