Abstract: The present disclosure relates to a heat not burn (HNB) consumable comprising an aerosol-forming substrate and a downstream filter having upper and lower surfaces spaced by opposing longitudinally-extending transverse surfaces wherein the filter has a greater width than depth. The filter may comprise at least one inwardly-extending air flow path extending from at least one of the upper, lower or transverse surfaces. At least one of the surfaces may be a curved or rounded surface or comprises a curved or rounded surface portion.