Well, if you got 'em at a store, hold on to your receipt and just bring 'em on back within 90 days, and it's a no questions asked return.
I always seem to have a harder time sizing up allen keys than wrenches or sockets, so unless it's an unusually large or minuscule size, When I don't want to rummage around my toolbox drawer full of random keys and sets, I tend to grab for the little three buck metal folding
Metric and
SAE key sets I keep together. They're beefy enough to give you pretty fair purchase and leverage too. I even cannibalized one just for the two of its keys most often needed on my Norton (fuel cap mod) and Amphicar (carb's inset flame arrestor retaining screws, which constantly rattle loose) respectively. Once easily unscrewed, the set's curve-ended keys dangle nicely on a keychain...