A liquid direct injection assembly includes a direct injection supply kit to mix liquid components into a mixture and deliver the mixture to a treatment device. The supply kit includes one or more liquid component containers that each include an elongated flexible bladder and a discharge nozzle to discharge a corresponding liquid component from the bladder. The supply kit also includes one or more metering bodies each defining a metering orifice to control a flow rate of the corresponding liquid component from the bladder. The liquid direct injection assembly also includes a container tray configured to removably support a liquid component container.