Welcome to the SuperDuo craziness! There are many sizes and shapes to SuperDuos. They are all pressed glass - so that they are more consistent in size and shape. They all have two holes. They all are somewhat oval in shape. But there the similarities end!
There are at least four versions of SuperDuos, with the possibility of more to arrive on the market at any time. SuperDuos were created after Preciosa released the Twin beads. Twin beads can be irregular in size and shape, making it very frustrating for beaders to use them in designs. SuperDuos are made with a pressed glass process that ensures more uniform size and shape, making them much easier to use. While I've seen some designs incorporate the various versions/sizes of SuperDuos, I recommend that you stay within the colors available in each variety for more uniform designs.