Swauber applicators are a must have for any shop toolbox or workbench. Use them for applying gun blue chemicals such as plum brown. perma blue gun blue and super blue gun blue. Or. use them to apply any firearm cleaning products such as bore scrubber 2-in1 bore cleaner. barricade protectant and rig rust protectant. Any job that requires the application of a liquid product. the swauber is the right tool for the job!