The ones shown here were tied on TMC T400 hooks. These are , as far as I know, only available in sizes 10, 12 and 14 (so not that very small). But it's form looks as if made especially for it. If interested I can post two patterns (Montana-type and Pheasant tail type) with which most nymphs can be adapted to this "bubble-type".
Íf you are gone use them I would like to know about your results.