What are you planning to use these tiny little servos for? They were designed to run RC toys, and they're really small, weighing only a couple of ounces or so. I suppose you could power a very small CNC machine with them, but it doesn't seem worth it, considering that you'd have to come up with a power supply that put out current at 300hz.
It looks like they're set up to run a timing belt, but you can probably pull off those pulleys and use any coupler you wanted.