Our most popular essential oil diffuser necklace makes a dainty-yet-noticeable addition to any outfit. These "cheerio" necklaces are made of durable stoneware and are strung on a solid sterling silver chain. Adjustable chain 16"-18". Charm size: 1/2"x 1/4" . Each charm variation is handmade and is coated with our glaze on one side; the smooth back surface remains unglazed. This open-back surface is designed for diffusing essential oils (or perfumes). The ceramic bead becomes warm as you wear it, and in turn, the aroma of the oil will be released. One drop of Peppermint on the back and I experience all-day "peaceful bliss" fragrance!