Review: The Heat Company Handwarmers
The Heat Company Handwarmers
Normal warmers with extravagant marketing claims
These are perfectly ordinary disposable handwarmers. Nothing wrong about them per se.
In and out of the packet (Own work. License: CC-BY-SA.)
Except with the marketing, of course. They claim that these last for 12 hours. Maybe with a precise thermometer you might detect some faint memory of heat radiating from these after 12h, but in practice these become useless at around 6 hours, that is the normal time for other brands as well.
So these warmers are no worse than others, but doubling the time claim is just cheating the customer. I recommend supporting a vendor with more realistic claims.