You need a Catan® game (aka The Settlers of Catan®) in order to play with this extension.
Now five to six players can explore and settle Catan!
In the Catan: 5-6 Player Extension™ you control a group of settlers exploring and taming the uncharted lands of Catan. Embark on a quest to settle the rich island, competing against more opponents for added fun. Add 1-2 more friends or family without sacrificing ease of play. Add green and brown settlers and expand your island with 2 more harbors and 11 unique, new terrain tiles.