An extension for building set number 26 (26A) includes 291 stone blocks in the three standard colors; brick red, natural sand, and slate blue. The Designs for Architectural Models booklet includes ten building plans for large and complex buildings including a Russian cathedral, Vienna resort hall, and a Turkish mosque. Packaged in a traditional wooden box for storage with a packing diagram and construction templates. This expansion allows you to build larger and more complex models. This set plus the combination for set #26 becomes the equivalent of set #28 and allows you to build all of set #28 models.