This set pairs the Lock Box with a coordinating insets tray, offering a natural extension that allows children to work with multiple lock-and-key correspondences in a single, organized presentation. The tray format encourages sequential work and supports order, a key Montessori sensitive period, by giving each piece a defined place. It is a practical upgrade from the standalone box if you want to extend the lock and key work across a broader range of fine motor challenges without sourcing separate materials.