Apparatus and method for mixing and dispensing components of a composition

A cartridge assembly used with a conventional caulking gun for mixing and dispensing components of a material. The cartridge assembly includes a component carrying body that has a plurality of separate component reservoirs and a component flow directing housing at a forward end of the reservoirs. A mixing unit extends between the component flow directing housing and a discharge nozzle secured to the front end of the carrying body. The mixing unit mixes the components and delivers them to the discharge nozzle. The mixing unit includes a plurality of mixing cylinders that each have a longitudinal axis that extends substantially parallel to the longitudinal axis of the component carrying body. The mixing cylinders and guiding channels that extend between them form at least a portion of a component mixing path. The mixing cylinders can each include one or more mixing elements.