We recommend that, one essential oil for one time, to avoid flavor smell mixing.Size: 35mm in diameter X 15mm in height (without clip height)The amount of essential oil dropping into the aromatherapy wood is up to you and the style of your essential oil, usually 3-5 drops is enough.A special gift ideas with good design and purpose for aromatherapy fans and anyone who loves essential oil. As time goes by, it's function will gradually increase. The aroma will also last longer and longer!!