I just picked up two pairs of XS Fives for REALLY cheap ($10 each). They're kinda beat up and the lenses have some scuffs. I want to replace/cut new lenses as i don't want to screw up my son's vision and want to get him started off right with collecting and taking care of his glasses.

I know the base curve is 8.75. Just wondering how one determines which "donor lens" to use? And if you can list what lenses I can use, that'd be great too!

First pair is the Black/Blue Iridium
Second pair is the Berry/Grey

It's not required that i use the same colored lenses. If anything i'd like to use a Emerald or Jade in the Black frame and a Fire or +Red in the Berry frame.

I don't have first hand experience, but since they're so small, I would imagine you'd have a wide array of choices. Knowing the base curve puts you in a good position. I think the only thing you'd want to ensure, is that there's enough room when holding the lens in the proper position. You can always make a lens fit within the dimensions of another, but you also want to make sure the XYZ remains in effect.

chop cut some fire lenses for my son's XS Fives. so he definitely will have the answer to your question.