Retention hours only compare when the stated conditions match · review
The narrow-mouth Iron Flask, which pours cleanly and will not take a bottle brush — and the only listing on this shelf whose maker rules out the dishwasher outright.
A 32 oz narrow-mouth bottle with a carabiner straw lid.
IRON °FLASK states double wall insulation that keeps the bottle sweat-free, with drinks cold for up to 24 hours and hot for up to 12; a leak-proof carabiner straw lid that clips onto bags; and 18/8 premium stainless steel, BPA-free and non-toxic, stated never to leave a metal taste or rust, with the instruction HAND WASH ONLY WITH SOAPY HOT WATER. The remaining two bullets are about gifting.
No conditions. No mouth figure. No base figure. No seal availability. No weight.
Pours clean, holds heat.
This shelf’s introduction divides the shelf on this one specification. A narrow mouth pours into a cup without slopping and loses less heat each time it is opened. A wide mouth takes ice, soup and a bottle brush.
No listing on this shelf publishes a diameter. This one at least says which kind it is.
The two instructions fight each other.
Three listings on this shelf of fifteen say anything about washing, and all three are American.
The Thermos flask in this group says dishwasher safe, top rack recommended. EcoVessel: flask and cup both dishwasher safe. This one: HAND WASH ONLY, in capitals.
A hand will not go through a narrow mouth. Expect cleaning tablets and a long-handled straw brush.
On its own other listing.
Iron Flask states that only its 14 oz, 18 oz and 22 oz bottles fit cup holders.
This is 32 oz. This shelf’s buying tip asks you to check the base against your holder before buying, and no listing on this shelf publishes a base diameter — so that sentence is the closest thing to one that exists here.
The American Amazon store was listing it at about $9 at the time of writing.
Every figure here is what Keepa held on the day this page was last revised. Offers and prices shift without warning.
Prices quoted in this text were read on October 8, 2026. The live price is at the top of the page.
| Capacity | 32 oz — stated, about 950 ml. The maker’s own wide-mouth listing states that only its 14, 18 and 22 oz versions fit a car cup holder, so a 32 oz bottle from this range does not |
|---|---|
| Wall construction | Double wall insulation — stated, and credited with keeping the outside sweat-free with cold drinks. No vacuum is named in so many words, and no layer count beyond two |
| Steel grade | 18/8 stainless steel — stated as premium, BPA-free and non-toxic, and stated never to leave a metal taste or rust. The AISI number behind 18/8 is not given, where one listing in this group names 304 |
| Hot retention | Up to 12 hours — stated. It is the common figure on this shelf: several of the twelve listings here claim 12 hours or less, and one claims 18 |
| Cold retention | Up to 24 hours — stated. The standard claim across this shelf |
| Retention conditions stated | Not published — no starting temperature, no ambient temperature and no threshold that still counts as hot. No listing on this shelf publishes them, which is what the hub’s own summary line is about |
| Mouth diameter | Not published as a figure, but the mouth is stated to be narrow, which is the useful half of the answer. This shelf's introduction sets out the consequence: a narrow mouth pours cleanly and loses less heat, and will not take ice, a bottle brush or soup. No listing on this shelf publishes a diameter |
| Lid type | A carabiner straw lid — stated leak-proof, clipping onto a bag by its own carabiner. One lid is supplied, where the maker’s wide-mouth listing supplies three |
| Seal availability | Not published. No listing on this shelf says whether replacement gaskets can be bought, although this shelf's introduction notes that a flask usually outlives its first gasket by years |
| Base diameter | Not published as a figure. The maker states on its own wide-mouth listing that only the 14, 18 and 22 oz bottles fit cup holders — which is the nearest thing to a base figure anywhere on this shelf, and it excludes this 32 oz bottle |
| Finish | Not stated on this listing beyond a choice of colors. The maker’s other listings describe a powder coat |
| Empty weight | Not published. No listing on this shelf publishes one |
| Amazon reference | B0F1TH1JH1 |
| EAN | 0850026774832 |
It is the real decision on this shelf, and this shelf's introduction sets out both sides. A narrow mouth pours cleanly into a cup and loses less heat every time it is opened, which is what you want for coffee or tea on a cold walk. A wide mouth takes ice cubes, soup and — crucially — a bottle brush. This is the narrow one, and the maker says hand wash only, which puts the two facts together badly: you must wash it by hand, through an opening a hand will not fit. Plan on cleaning tablets and a long-handled straw brush.
No, on the maker’s own evidence. Iron Flask states on its wide-mouth listing that only the 14 oz, 18 oz and 22 oz versions fit cup holders — a 32 oz bottle from the same range is not among them. That sentence is worth more than it looks, because no listing on this shelf publishes a base diameter at all, and this shelf's buying tip asks you to check the base against your cup holder before anything else. Here the maker has answered it for its own range, and the answer for this size is no.
It is one of only three cleaning statements on this whole shelf, and it is the restrictive one. Two listings in this group state the opposite — Thermos says dishwasher safe with the top rack recommended, and EcoVessel says both its flask and its cup are dishwasher safe — and the nine European listings here say nothing either way. A dishwasher refusal usually protects a powder coat or a printed finish rather than the vacuum, and the instruction here is specific: hand wash with hot soapy water. Through a narrow mouth, that is the chore you are accepting at this price.
Close prices, same category: comparable camping gear. We keep only the specifications all of them publish, because a column with gaps compares nothing.
| Model | Price | Capacity | Wall construction | Steel grade | Hot retention |
|---|---|---|---|---|---|
| IRON °FLASK 32 oz narrow mouth | $9 | 32 oz — stated, about 950 ml. The maker’s own wide-mouth listing states that only its 14, 18 and 22 oz versions fit a car cup holder, so a 32 oz bottle from this range does not | Double wall insulation — stated, and credited with keeping the outside sweat-free with cold drinks. No vacuum is named in so many words, and no layer count beyond two | 18/8 stainless steel — stated as premium, BPA-free and non-toxic, and stated never to leave a metal taste or rust. The AISI number behind 18/8 is not given, where one listing in this group names 304 | Up to 12 hours — stated. It is the common figure on this shelf: several of the twelve listings here claim 12 hours or less, and one claims 18 |
| EcoVessel 8 oz with shot cup | $10 | 8 oz — stated, about 240 ml, with a separate 3 oz silicone cup that fits into the base. It is the smallest capacity on this shelf by a wide margin, where the rest run from 16 to 40 oz and the European side reaches a liter | TriMax triple insulation — stated by name. It is the only triple-wall claim on this shelf; every other listing here states a double wall, and this shelf's introduction opens on the assumption that the physics is shared. No layer materials are described | Not named. Food-grade stainless steel is stated, described as rugged, and no 18/8 or 304 figure appears | Not published separately. The listing states that drinks are kept at the perfect temperature for up to 24 hours, without saying whether that applies to hot, to cold, or to both — and this shelf's introduction notes that each figure comes from conditions the maker sets |
| Mont-Clair 500 ml double-walled flask | $8 | 500 ml — stated in the title | Double-walled insulation — stated; the listing does not use the word vacuum | Not published on the listing — the flask is called 100% stainless steel, with no grade named | Not published on the listing — the listing says drinks are held hot or cold, with no number of hours |
| Fanhaw 40 oz, three lids | $12 | 40 oz — stated, about 1.18 liters. The listing adds that 18, 24, 32, 40 and 64 oz versions exist, which confirms that capacity is a variant of one listing in this category rather than a separate product | Advanced vacuum insulation — stated, with no layer count. The word vacuum is used, which two listings on this shelf avoid | Not named. Food-grade stainless steel is stated, with resistance to rust, dents and odors, and no 18/8 or 304 figure. It is the only American listing in this group not to state 18/8 | 12 hours — stated. The common figure on this shelf |
Someone who pours rather than scoops, and does not mind washing by hand
Amazon reports what buyers took in the month before this page was last checked: at least 100.
The figure is a floor, rounded by Amazon, and read through Keepa — it says what buyers picked, not what a maker claims.
Specifications: the manufacturer sheet for camping and hiking gear and the matching Amazon product page. Prices and availability: Keepa. Every figure on this page names its source.
1 liter · 18/08 stainless · 13 h temperature stability stated, hot and cold not separated · bottle brush, jute bag and carabiner supplied
A 1 liter flask supplied with a natural-bristle brush and a carabiner, whose single retention figure of 13 hours is never split into hot and cold.
Best for: A liter bottle bought with its brush and its carry loop, where cleaning matters more than a comparable hours figure.
≈ $33
500 ml · vacuum insulated · SUS 201 outside and SUS 304 inside · 24 h cold and 12 h hot stated · brushed finish · top handle
The only flask here that names a different steel for the inside and the outside, alongside a stated vacuum, both retention figures and a brushed finish.
Best for: A day out where a named inner steel, a stated vacuum and a dishwasher-safe body matter more than the hours quoted.
8 oz · TriMax triple insulation, the only triple-wall claim here · food-grade stainless, grade not named · 24 h stated once, hot and cold not separated · removable 3 oz silicone cup · folding hidden handle · dishwasher safe, flask and cup
The only triple-wall claim on this shelf, on an eight-ounce flask with a removable three-ounce silicone cup in its base — and a single 24-hour figure that does not separate hot from cold.
Best for: A hip-pocket flask for spirits or a single coffee, where two can share from one cup
≈ $10
