Part of GSI's Boulder line, which is their shatter-resistant plastic drinkware — the number is the capacity, so this is the 10 fluid ounce one. Copolyester body with a grippy silicone bumper, 3.7 x 1.1 x 6.5 inches, and it weighs 4.1 ounces empty.

The features that earn their place: a wide mouth for easy filling, pouring and drinking; molded graduation marks so you can measure what is in it; and a hinged silicone cap that stays attached — GSI's phrase is “impossible to misplace,” which anyone who has lost a cap in long grass will appreciate. BPA free.

Read this before you buy it as a hip flask, because it is not one. It is six and a half inches tall and just over an inch thick, with a wide drinking mouth and measurement graduations. That is a slim bottle, not a pocket flask. GSI call it a flask and we have kept their name, but if you want something flat for a back pocket with a shot-glass cap, our 10 fl. oz. Hip Flask is that product.

The graduations and the wide mouth make it genuinely useful for things a hip flask is not: measuring out fuel for a stove bottle, carrying oil or a mixer, a measured dose of anything. GSI do not state it is insulated, so it is not.

Care and one GSI caution

Hand wash with warm, soapy water and dry thoroughly; avoid abrasive cleaners. GSI's warning, in full: “Flask designed for travel/outdoors use. Long term storage of liquids may affect flavor.”