Carbonation and Line Cleaning Ball Lock Quick Disconnect (QD) Cap - Stainless - Duotight Compatible. This stainless steel ball lock cap features soda bottle threads, allowing you to convert a soda bottle into a pressurizable growler. It is compatible with both gas and liquid ball lock disconnects. Also works well for cleaning draft lines. Simply add line cleaning solution to a soda bottle, attach it to the draft line, and open the faucet to push solution through. This version features a 6.5mm Duotight compatible stem. Use the 8mm or 9.5mm reducer to attach EVABarrier draft line. 28mm PCO 1881 Threads. Please note: The threaded section of the bottleneck must be at least 1/2" long to form a seal. These caps are not compatible with the KegLand 500mL PET Bottles.