Designed to be used with GLASSHOUSE FRAGRANCES Scent Stems™. Place your Scent Stems™ of choice into the metal vessel, ensuring it's placed on a flat surface away from open windows or vents. Scent Stems™ are sold separately. We suggest replacing your Scent Stems™ every 30 days to refresh your fragrance or to increase its strength. After 30 days, the Scent Stems™ can be placed in recycling with other paper products.