XL Polydron is four times the size of Giant Polydron and so the 2 systems are compatible This set just contains XL Polydron which is great for building castles, princess's towers, cars, boats, and houses with tunnels to crawl through. Children will be able to build large constructions, whilst all the time learning about shape, 2 and 3 dimensional objects, texture, team-work and role play. They will work together to put their ideas into reality. All the pieces in this set are supplied in 4 colours . Age: 2+