Flasks · half a litre
Same volume, same stated hours — what is left to separate two 500 ml vacuum flasks?
These two publish identical headline figures: 500 ml, 12 hours hot, 24 hours cold, double-walled and vacuum insulated. Six of the nine lines below are therefore ties, which is the honest result and also the point of the page. Neither states a starting temperature, an ambient temperature or a fill level behind those hours, and neither does any of the nine flasks in this hub, so the numbers cannot be read against each other.
| Compared on | 500 ml vacuum flask, SUS 201 outer and SUS 304 inner | 500 ml vacuum flask, 18/8, with a cotton sleeve |
|---|---|---|
| Capacity | 500 ml — stated | 500 ml — stated |
| Wall construction | Double stainless shell with vacuum insulation — stated, and stated safe with carbonated drinks | Double-wall vacuum insulation — stated, and stated to reduce condensation outside |
| Steel grade | SUS 201 outer shell and SUS 304 inner shell — both stated | 18/8 stainless steel — stated, described as food grade |
| Hot retention | 12 hours — stated | 12 hours — stated, quoted for coffee |
| Cold retention | 24 hours — stated | 24 hours — stated, quoted for water |
| Retention conditions stated | Not published — no starting temperature, ambient temperature or fill level is given behind either figure | Not published — no starting temperature, ambient temperature or fill level is given behind either figure |
| Lid type | Removable screw lid with a full-jacket gasket, stated leak-proof, with a carry handle on top | Screw cap — stated, described as helping to prevent leaks |
| Finish | Brushed stainless steel — stated | Not published — thirteen colours are offered and a cotton sleeve supplied; the coating is not named |
| Empty weight | Not published | Not published — described as lightweight, with no figure |
Each tick belongs to its own line and nothing more. The row of ticks is not a score: the two verdicts underneath settle the page, because these two answer different questions on the trail.
The Arendo is the only flask in this hub to state a different steel inside and out, SUS 304 within and SUS 201 without, and it is the one here that describes its closure — a removable screw lid with a full-jacket gasket and a handle on the top. Where the two publish the same hours, this is what is left.
The Nuactiv states the same 500 ml and the same 12 and 24 hours, names 18/8 steel and arrives with a cotton sleeve and thirteen colours to choose from. It calls itself lightweight and publishes no weight, and its screw cap is described rather than specified, which is why the closure line goes the other way.
Nothing published here settles that. Both makers state 12 hours hot and 24 cold, and neither states the starting temperature, the ambient temperature or the fill level those hours rest on. Two unconditioned figures that agree are not a match, they are two claims that happen to be the same size.
The two listings do not put it in comparable terms. Arendo names two grades, one for each shell; Nuactiv names one grade for the flask. The extra information is on Arendo’s side, which is why that line goes to it — the line records who published a grade for what, and not a metallurgical ranking.
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.
≈ 13 €
500 ml · double-wall vacuum · 18/8 stainless · 24 h cold and 12 h hot stated · screw cap · cotton sleeve supplied
A 500 ml vacuum flask that names 18/8 steel and both retention figures, ships with a cotton sleeve, and calls itself lightweight without publishing a weight.
Best for: A commute or a day walk where a sleeve and a plain screw cap suit better than a straw or a flip lid.
≈ £12 / 10 €
Prices in these summaries were read on the dates each review gives. The live figure sits beside every product.
