An extension for building set number 24 (24A) includes 305 stone blocks in the three standard colors; brick red, natural sand, and slate blue. The Designs for Architectural Models booklet includes nine building plans for large and complex buildings including a palace, court house, a cathedral, and a chateau with doorkeeper's house. 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 #24 becomes the equivalent of set #26 and allows you to build all of set #26 models.