An architecture from the beta class (arbitrarily using the CATH hierarchy..). It includes the proteins green fluorescent protein, cyclophillin and porin. These are three different topologies of the architecture - in other words, the strands are connected in a different order. For GFP at least this is a very stable fold since the sheet is a continuous curve that is connected all the way round. This design can also be a large range of sizes - it scales well.