Each Decoder wheel provides a quick & easy references by just turning one of the 4 dials. The Practical Aromatherapy Decoder for Home and Garden wheel provides quick & easy reference for the use of essential oils around the house and in the garden for: cleaning and disinfecting, repelling insects and pests, getting rid of mold on plants, deodorizing, creating scents for the home, etc. Approximately 6" x 6" x 1/4".