Once your diffuser has run out, you don't have to buy a whole new diffuser, just purchase our refill bottles which come with 200ml of diffuser refill. Our largest diffusers are 200ml so it’s the perfect size. Our mini luxe diffusers are 120ml so you will be able to fill these almost twice! Don't forget to also purchase a new set of reed sticks when you're refilling your diffuser or after about 6 months to keep your diffuser fresh and dust free.