10 inches diameter was recommended, I think I may have used a few nine inch ones, with one seed potato per pot. They worked very well, producing two-three portions per pot, much better than the second year when I used larger containers and got fewer potatoes. They are also easier to move around, so I could plant them early in the season, put them out during the day and bring them under cover at night. I grew Vivaldi last year and they were great.