Abstract: The metered discharge of aerosol compositions from aerosol dispenser packs through an ordinary aerosol valve is achieved with precise control over both the amount discharged during each metered discharge operation and the specific time interval available between each metering operation by causing the aerosol composition to traverse a closed path from the body of the aerosol pack to the discharge orifice through a plug fitted into the tailpiece of the valve, the plug comprising a variable length of a reticulated porous polymeric material having an average pore diameter of less than 10 microns with the pore volume being between 10 and 50% of the plug. The plug is fitted to the tailpiece of the valve which enables uniform spray characteristics to be obtained.