Twin packs are a convenient way to make sure you always have a reserve on hand so you never run out. Plus, they make it easy to enjoy your favourite authentic, true-to-life Yankee® scent in multiple locations. Refills last for 4 – 6 weeks. Clean Cotton is Sun-dried cotton combined with green notes, white flowers, and a hint of lemon.. Use only with Yankee Candle® electric home fragrance ScentPlugs (sold seperately).