A blind box is a type of packaging that keeps its contents a mystery until it is opened. Designer toy blind boxes typically come in themed series, with the full range of possible items displayed on the packaging. Some items in a series may be rarer than others. The rarest ones are referred to as "secret," "hidden," or "chase" items. They are usually not part of the standard 12-box set and are only identified on the packaging by their silhouette. In sets that contain a "secret" figurine, one regular edition figurine is randomly replaced.