They have a very fine pitch on the threads and can get cross threaded making the bolt unusable. It will be best to have a 24mm socket or wrench, 

 

You do not want to get caught with your bike down just because you didn't have an extra drain bolt. 

 

Fits most new Vespa and Piaggio 4T engines 50cc to 500cc. Does not fit Piaggio BV350, Beverly 350.