Yep, sometimes "about" works as in it's "about" 3 inches in diameter. Other times "about" isn't close enough and more precise is needed. 2 i, for that chainring there's no excuse for describing it as one thing when it's not that at all. False advertising comes to mind but probably not worth the hassle of doing anything about it. So with those things in mind and if anyone is interested in either the Takeya or the Hydro Flask I used a micrometer!
Hydro Flask 18 oz without the sleeve measured near the base = 2.907" with the silicone sleeve 3.042
Takeya 24 oz without sleeve = 3.039", with the sleeve 3.175... apparently the sleeve is a bit thicker for this one.