Carcassonne Insert: - Rules of Play says:
Insert compatible with Carcassonne® and the first five expansions to the game: Inns & Cathedrals®, Traders & Builders®, The Princess and the Dragon®, The Tower®, and The Abbey & Mayor®. The insert also includes three bonus trays for use in one of the expansion boxes to store the Count, King & Robber®, Bridges, Castles and Bazaars®, Hills & Sheep®, and Under the Big Top® expansions.