A universal, fluid transfer, Q-D coupling assembly for connecting water supply hoses to fire-fighter's wild-fire backpack tanks comprising a two or three-part combination: #1) a ⅝″ female member having an axially-slideable detent collar and an internal, spring-biased fluid shut off flap, and #2) a male nozzle/reducer/collar member having a detent engaging groove. A ball valve is connected to element #2, either integral as #2A, or as a separate assembly element #3. Both elements #2 and #3 have a female threaded collar that receives the nominal 1″ male fitting of a garden hose. The parts can be supplied as a kit. Element #2 is a unitary fitting combining a hydraulic-sized, male Q-D nozzle, a reducer section and a standard garden hose-sized, female internally-threaded fixed collar. This element is preferably supplied with an integral ball valve intermediate the reducer portion and the female collar.