I did get a bargain last year on some Allen keys.
Went to use them once and realised why. Imperial. FFS.
I hate to admit it but I bought a set of Allen keys many years ago
they are in a sort of yellow plastic case and fold out - very well designed and well made
it was basically the only set I have used much - so no experience of using any others
I had been wondering for many years why thy never seemed to fit properly - I would try several and use the one that fitted best but it was never perfect -- I just assumed that they were all like that
a few months ago I got them a bit mucky when using them to dismantle the gears on my bike and found the sizes were on the case
in imperial
and those years wondering why they never fitted properly!!!