This is a rather simple, but extremely effective way to fill growlers from your draft system! Going to a party, but don't want to bring a keg of homebrew? Filling straight from the faucet creates a lot of foam, and you lose carbonation. Simply plug this filler into your faucet, attach some 3/8" tubing, and fill! This model is designed to fit standard (non Perl or Perlick) faucets, as their inner diameter is different than these other faucets. Faucet insert OD is 1/2"