Large photo of differnt size pots
Foreground: 29, 24 and 19 cm black plastic pots. Background: 50 cm glazed pot (left) and 48 cm Decor Roman self watering pot. 

While the black pots can be used to grow herbs and picking vegetables their small size means it is better to use them only for temporary plantings such as growing small plants in preparation for potting up into larger pots or planting out in the garden.  They can also be used  to make ground and edge pots.