StToddy ) - I went with the smaller gauge with 1/8"NPT , because after I cut off the very top of the applicator it would screw right into the applicator . ( I put silicon on the threads before I screwed it on and let it dry overnight . I try to keep things as small and lite as possibly so it is not to heavy and bulky . Also the applicator is graduated in size like the HE bulb . Steve ) - I like the idea of the gum stopper ( the more vacuum you apply into carboy the stopper would be pulled into the neck for a tighter seal ) . Maybe you could have 2 designs , (1) your basic one like you have now , (2) or a deluxe one with gum stopper , valve & cap , gauge ) .