An extension for basic set number four (4A) includes 65 stone blocks in three standard colors; brick red, natural sand, and slate blue. The design booklet includes plans for: an observation tower, a customs house, an Italian chapel, and 39 other models. Packaged in the traditional wooden box with a packing diagram. Useful for creative free-form building as well as building from the standard templates. Use to expand your building experience beyond starter set four. This set plus basic set #4 becomes the equivalent of set #6 and allows you to build all of set #6 models.