If you go to any immense retail store and try to find steel shot for waterfowl hunting, you will probably find BB, 2 shot, and 4 shot. Maybe.
These restricted options often leave you in a hard position. Early season usually involves shooting a lot of wood ducks and teenage puddle ducks, which are diminutive to medium-sized birds. You don’t want or need a No. 2 shot for these birds. A workable compromise is a No. 4 shot, but if you’re able to attract larger adult mallards, it’s a good idea to have a slightly larger shot. And for teals and wood ducks, you may want something a little smaller.