Aerosol provision systems

A cartridge for an aerosol provision system that comprises the cartridge, a control unit, and a vaporizer for vaporizing an aerosolizable material, the cartridge comprising:

• a mouthpiece outlet;
• an air channel extending from an air inlet for the cartridge to the mouthpiece outlet via an aerosol generation region;
• a reservoir for containing an aerosolizable material for aerosolizing;
• an aerosol outlet tube, extending between the aerosol generation region and the mouthpiece outlet, for directing aerosol generated in the aerosol generation region through to the mouthpiece outlet, wherein the reservoir extends around the aerosol outlet tube;
• and
• an aerosolizable material level observation structure for allowing a user to observe a level of aerosolizable material inside the reservoir, the aerosolizable material level observation structure comprising a portion of the cartridge, wherein the portion of the cartridge forms a first wall portion of the reservoir;
• and
• wherein a surface of the outlet tube is visible from the portion of the cartridge;
• wherein the cartridge comprises a first surface, a second surface, a first side surface, and a second side surface, wherein the first side surface and the second side surface are located between the first surface and the second surface;
• wherein the first side surface and the second side surface are inclined towards the mouthpiece outlet;
• wherein the portion of the cartridge:
• is located on both the first side surface and the second side surface;
• and
• further comprises:
• a first window for viewing into the reservoir, wherein the first window is elongate and is on the first side surface;
• and
• a second window for viewing into the reservoir, wherein the second window is elongate and is on the second side surface;
• and
• wherein each of the first window and the second window comprises a maximum dimension of no more than 20 mm;
• wherein the reservoir further comprises a second wall portion;
• and
• wherein the first wall portion comprises a first concentration of colored pigment, and the second wall portion comprises a second concentration of colored pigment, wherein the first concentration is less than the second concentration.