(5) Three Piece Airlocks Set of 5 Three Piece Airlocks. Use on your fermenter to help prevent outside air from backflowing. 3 Piece Airlock (Qty. 5) More Fermentation Related! Our Fermentation Related Reviews – Fermenters and More Yeast Starters and Fermentation Resource Page Yeast: The Practical Guide to Beer Fermentation Compare Prices: StirStarter Stir Plate More: Recent Amazon Finds