Crystals are used as a substitute for water to hold the Scentsationoil in a burner dish. You can re add your Scentsationoil to the crystals once used, although DISCARD the crystals when they turn black.
NBHeavy products at low cost and high weight can have a direct effect on your parcel postage cost. i.e. Bath Crystals, Burner Crystals each weighing at 0.5kg