Abstract: A chemical concentrate metering device 16 is provided for an agricultural or horticultural or forestry sprayer system including a reservoir 2 for supplying a dilutant and a spray head 10 for spraying a mixture of the dilutant and a chemical concentrate. The metering device 16 comprises a conduit 17 having an inlet 18 for receiving dilutant from the system and an outlet 19 for supplying a mixture of the dilutant and a chemical concentrate to the system. In addition a seating 22 is provided for detachably receiving a receptacle 31 for supplying chemical concentrate and an injection orifice 26 opens into the conduit 17 and communicates with an outlet 35 of the receptacle 31 received in the seating 22 so as to enable chemical concentrate to be injected from the receptacle 31 into a flow of dilutant in the conduit 17.