Cap for the typical 1lb throw-away/disposable propane/mapp gas tanks that have a 1" x 20TPI thread. Keeps partially used tanks from slowly leaking out when the valve sticks open. You'll need to supply a rubber gasket to use with the cap.

(FYI, Added a PropaneCap-mm.stl file because Cura didn't like the original which was exported in inches instead of mm).