I really like the concept of this pick, I am forever breaking thumb picks (and finger picks) by jamming them on my fingers too sharply, so a metal frame combined with a plastic blade seemed ideal.
Unfortunately the plastic blade seems somewhat "cheap" - it has fairly sharp, square edges, and it produces quite a scratchy tone. I've tried gently filing the edges with a fine nail-file, but if anything that seems to make it worse as the edge frays rather than smoothes. It's a real shame they didn't choose to use a more carefully rounded edge to the blade and a denser plastic.
(I'm playing on a steel string acoustic - it occurs to me that these might be more suited to a nylon-stringed classical, but I don't have one of those to test on. A quick test on a uke, the sound is much better).
I bought a medium size; I've got quite smallish to average fingers for a man but I was able to gently bend the metal to get them to grip better. You could bend the other way if you wanted them bigger.
The blade is also quite small, it doesn't stick out as far as most other thumbpicks, but that's a question of taste of course.
Having said all that, the metal construction seems good, they are comfortable to wear, and they grip the thumb nicely and don't move about. I don't see this snapping any time soon, unlike the plastic ones that break all the time.