Finisher Peroxide Treatment is Step 3 of 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, removes residual organic stains, and lightly sterilizes the surface. Finisher helps reduce water spots, mold and mildew odors, and permanently removes stains. Finisher breaks down into oxygen and water, leaving no chemical residue that requires further removal.