The specifications of the Dora Kalff Classic tray have been especially requested by Jill Carter Training and are also complient with the requirements for  AIST (Association of Integrative Sandplay Therapists) practitioners.
Plain sides are the preference for these trays as a way to leave the discovery of the blue less guided for the client. The shade of the blue and the soft rounded top edge of the tray as well as the branded mark being on the bottom rather than the side.