Pump VS hopper size
Here in the US open class pump any hopper size and constant air. this includes senario, rec play, and openclass tourny play. Stock,true stock, 12gram air system and stick feed that is parallel to the barrel. With few exceptions stick feed will hold ten rounds reloaded with ten round tubes. In some cases gravity feed stick tilted up ten rounds and parallel will be allowed 20 rounds. Depends on tournament rules. Most rec, senario, open play is open class as above. There is variations on this but this post whould become a book. Hope this helps some. I play all types including old time pistol. now that is truley stock.