The Hydro Flask Standard Mouth is especially reliable. It’s an insulated, double-walled stainless steel water bottle with a powder-coated exterior (the permanent, lightly textured coating) and a plastic cap. Unlike aluminum bottles, this one won’t dent easily. Unlike glass bottles, this bottle won’t have issues with the bottom cracking. And unlike plastic bottles, it won’t deteriorate quickly while in use.
If you tend to drink straight from the bottle, the Hydro Flask has a narrow, tapered metal edge. And it mimics the rim of a glass better than the lip on any other bottle we tested, including the round lip on the Klean Kanteen and the thick, industrial-feeling lip on the Yeti Rambler. The standard mouth opening is 1¾ inches wide—wide enough to fit ice but not so wide that water will slosh up your nose if you drink on the move.