Thanks to everyone who responded. I've now got 4" pots on the way. Margaret, didn't your soil blocker come with a recipe for soil to use in it? A lot of people swear by them. I've thought about using the medium and large size ones but it's one of those things about not wanting to spend the money unless I'm sure they're what I want (and how could I know that until after I buy and use them). I guess we're all still looking for the perfect container and the perfect medium to fill it with. Liz