Finisher Peroxide Treatment is Step #3 in the Double Black Interior Cleaning System. Finisher completes the system by adding a final attack on odor-causing molecules and organic stains. Finisher breaks down odor-causing chemicals, eliminates any residual organic stains and slightly sterilizes the surface. Finisher assists in reducing water stains, mold and mildew odors as well as finalized stain removal. Finisher breaks down into oxygen and water, leaving no chemical residue left that requires further removal.