I'm trying to make a bigger version ofThe original baby bottle's wide open like a cup. It's genius!It only holds 8 oz. though, & let's be honest; that just sucks! I'm a high-volume drinker, but almost never the hard stuff.I'd prefer to be constantly be sipping on something. I love the nipple's shape,& it's vented so no air gets in my belly! Both are ComoTomo. I'd pair it with a 32 oz. Nalgene ATB sports bottleYou can see exactly how many ounces are in it, just like the baby bottle. It's also the only microwaveable, squeezable one I've found, which the baby bottle also has going for it, but the sports bottle may be less cup-like & harder to clean.Another issue I have is that the baby bottle has a 2.55" rim, & a 3" ring, once it & the nipple are on the thing. Is that understandable? The sports bottle's lid is only 2.48." Will it work? If not, how do I make up the difference in size?