The Reed Fragrance Diffusers are oil-based, with added essential oils and no alcohol, so they evaporate slowly and lasts for much longer than other products in the market (up to 6 months for 250mL bottles, and up to 1 year for 1L refills on the large diffuser bottles). Our diffusers? signature bottles are hand blown in Portugal by glass artisans, exclusively for Castelbel and Portus Cale, to give a touch of exclusivity to any home decor. Many professional interior designers/decorators and furniture manufacturers are our customers, because our diffusers are very nice decorative pieces and can create a more pleasant and cozy environment at any home/office/hotel. The bottles and fragrance are created by artists in UK, Switzerland and Portugal and are used by shops/hotels to create a unique ‘fragrance fingerprint’. The stopper is made of cork, a natural material grown in Portugal. It must be extracted in the same way as the cork in a wine bottle: by rotating it (not by pulling it), until it has been totally removed Fresh refills are not to be added to used oil. Any oil remains in the bottle shall be left to evaporate. The bottle must then be washed with alcohol or acetone (never with water!) and new reeds shall be used. . 250ml diffusers are perfect for perfuming bathrooms, bedrooms and small rooms. For wider areas, we recommend using the larger bottle with 1L refills. The 250mL bottle lasts up to 6 months and the bigger bottle (with 1L refill) lasts up to 1 year. You can buy refills instead of buying the whole bottle – saving money.