Will these fit costa Del Mar reeftons?

I wanted to let you know I reviewed and gave measurements of UKE strap under GAGardener03. This is part of it: The strap allows the sunglasses to easily be put over my head AND my sunglasses don't hang low on my chest (a fact that I appreciate). You have an approximate 15 inch length between the two (2 inch) areas that attach to the temple tips. * For a total of 19 inches ... but depends upon how far up you push the two temple tips on your bows. No idea what type of temple tips/bows you have, but I have triangular ones. It was an effort to get them on, but they work just fine.

Will these fit aviator frames?

It will fit any frame but check the aviator ear pieces. My wife's slide off if you pull on it a little.

Do they fit Persol sunglasses?

I don't know, I have Raybans and they fit perfectly. They fit like a Croakie would.

Will the ukes fit a 10 yr old's clear rx glasses? She will be kayaking and needs glasses to see, but they need to float if dropped in water.

These will float, but I have found that they also tend to slip off. The inner portion of the strap is not "sticky". it is fabric and does not grip well. I really have not used mine because of this. It is really annoying how they kept falling off. There may be better solutions for your 10 yr old.