Special OVERSIZE screws for Super Feeder extensions, lid or 1.5 gallon hopper.  These screws are the same 4-40 type thread but are slightly longer at 1/4" instead of 3/16"  These screws can be very handy if wanting to completely lock the extensions, lid or hopper in place due to very mischievous pets.  If using these screws, you will need to use a 1/8" drill bit to drill a hole through the half-moon recess in the part the extension, lid or hopper is being fitted/slipped on  SO THAT THE SCREW END WILL PROTRUDE THROUGH IT COMPLETELY.  Do not drill out the existing threaded small hole in the extension, lid or hopper! Using these screws, metal washers are not needed.

http://www.super-feed.com/extensionhalfmoonnote.htm