Great for hanging in cars or other small spaces, these oil diffusers harness the power of scent with coordinating crystals. Diffusers are made of glass with wood diffuser top. To use, simply remove diffuser top, remove the plug sealing the bottle, replace top and quickly tip over to infuse wood with scent. To refresh scent, tip again. Last approximately 3 months depending on temperature of environment, and is refillable for continued use.