These Alcyon 5236 Universal Joint Handcuffs are the better, robust version of the last Alcyon I overviewed.
These work with normal keys without needing specifically Alcyon keys which are unable to be purchased separately. Essentially if you have seen my early video on the chain link handcuffs, these are identical only with the universal joint instead of a chain.
I do like these a lot. My pair are pretty stiff because I have not had time to break them in yet. But the tolerances are quite good, for Alcyon.
If you want a cost effective ~ €20 pair of sturdy handcuffs that do not restrict TOO much, then these would be a great option.