If you have lost the cap to your growler, but dont feel like buying an entirely new vessel then grab a couple of these replacement growler caps. Made of black plastic with a poly-cone liner inside, the caps fit most standard size (64-ounce) glass growlers. Replacement growler caps are also great for breweries, distributors, and any other establishment selling and filling growlers. In stock and ready to ship. Features: Made of black plastic with a poly-cone liner inside. Fits most standard size glass 1/2 gallon (64 oz.) sized growlers. 38mm threading. Specs: Cap Diameter: 1 1/2".