I can vouch for the space saver cup. I have one in my nalgene pouch and it is good to go. The only problem is that it is a tight fit on the lexan bottles. The other (white bottles) slip right in. But, on the flip side, it does keep the bottle from coming out of the pouch!!

Garrett
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On occasion of every accident that befalls you, remember to turn to yourself and inquire what power you have for turning it to use. - Epictetus