Sometime I might not be able to so I've embarked on teaching my husband how to change the bag. Showed my preferred method, stressed importance of closing the bag and showed him the tupperware snap and realised I had mismatched flange and bag. I ordered mismatched stuff in the smaller size range. Thankfully I have some of the larger size left and some one piece in the larger size. I ordered cut to fit 1 3/4 flanges and the bags were 1 3/4 openings... At least it meant I could show him how to install an Ostovent on the bag since my old large stuff is ventless.