Abstract: A device for blending together components which are to form a given plastic material. The device has a stationary housing formed with inlet ports to receive the components which are to be blended together. Connected with the stationary housing is a removable cartridge having ports which receive the components from the inlet ports of the stationary housing. The ports of the stationary housing communicate with a mixing chamber of the cartridge in which there is a rotary impeller for blending the components together, the removable cartridge terminates at its front end in a nozzle through which the blended components are discharged. The impeller is driven by a shaft which extends rearwardly through and beyond the cartridge housing to connect with a drive carried by the stationary housing, the cartridge having a rear bearing portion situated in a bore of the stationary housing.