The opening of the pots have the following diameters:

Size: D13xH11, diameter pot opening: 10.5cm

Size: D16xH14, diameter pot opening: 13cm

Size: D20xH16, diameter pot opening: 16cm

Size: D23xH19, diameter pot opening: 19cm

Size: D34xH28, diameter pot opening: 28cm

Size: D45xH38, diameter pot opening: 38cm

Size: D56x47, diameter pot opening: 44cm

To be 100% sure the pot is waterproof, we recommend ordering a waterproof inner lining as well.