My understanding of the 3U cubesats that these are intended to be used on was that they weren't much bigger than a 2 litre bottle. Am I way off in my understanding, or do these just use most of the available volume?
A volume of 2 litres therefore implies a 2U unit, in other words 20x10x10 cm (the actual dimension of the 20 cm part can be chosen arbitrarily).