An induction heatable cartridge for use with an induction heating assembly, the cartridge comprises a solid vaporisable substance and at least one ring-shaped induction heatable susceptor held within and surrounded by the vaporisable substance. The susceptors are held in position such that, when the cartridge is positioned in an induction circuit in use, different regions of the outer edge of the one or more susceptors are at different distances from the induction circuit to provide different heating characteristics in the different regions. The centres of each of the at least one susceptors are aligned along a common axis.