They're 6mm quadcopter motors in the pictures. Very much only good for their intended use- not very efficient, and extremely low torque/high speed.

Try searching for '12mm mini gearbox' on ebay or the web and you'll find some useful stuff. What you really want is a 6mm planetary gearbox motor- they're tough to source at a decent price, but we're working on that(slowly).

Thanks,
Ben