Each Decoder wheel provides a quick & easy references by just turning one of the 4 dials. The Advanced Aromatherapy Decoder wheel provides 94 listings in these categories: Illness, work, body care, home use, animals and fun. Turn the wheel to find essential oil blending recipes. Specific blends are recommended for each listed need - such as a blend for PMS, another for cuts, etc. Whenever possible a number of alternative oils are listed. Approximately 6" x 6" x 1/4".