Best/most cost effective – complete range of allen keys?

Got an old frame with a recessed bolt that I can’t seem to get the usual suspect allen keys to fit?

Is it an imperial size? Or maybe torx?

It’s a late 70’s or early 80s frame, I tried torx, it’s allenkey as far as I know?

Probably imperial then.

cheers, going to order a set, unless I can find one that fits out of my parents old toolbox.

Don’t mix them up! If you do find some imperial ones mark them up with red tap so you know to to use them on metric stuff.

I’ve got this set…

Screwfix Allen keys

For less than a tenner it covers most bases.