A cartridge (2;200) for an aerosol provision system (1) comprising the cartridge (2;200) and a control unit (4), wherein the system comprises a vaporiser for vaporising an aerosolisable material. The cartridge (2;200) comprises an air channel extending from an air inlet (50) for the cartridge (2;200) to an outlet (60) via an aerosol generation region, and a reservoir (31) for containing aerosolisable material (207) for aerosolising. The cartridge (2;200) further comprises an aerosolisable-material-level observation means (205) for allowing a user to observe a level of aerosolisable material (207) inside the reservoir (31). The aerosolisable-material-level observation means (205) may comprise a portion (208) of the cartridge (2;200), which may comprise a window (210) for viewing into the reservoir (31). The portion (208) of the cartridge (2;200) may be located on a first side surface (209C) and a second side surface (209D) of the cartridge (2;200), and/or might be located on a different surface (209A;209B) of the cartridge (2;200).
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