Otis Technology, Otis Foaming Bore Cleaner, 3oz WARNING Warning WARNING WARNING: Cancer and Reproductive Harm - www.P65Warnings.ca.gov. Expanding Foam Ensures a Complete Clean Simple to Use Product Description Let expanding foam and time do the hard work in cleaning your firearm. Foaming Bore Cleaner easily cleans your bore. Simply spray in the breech end and the foam will expand to fill the bore and ensure complete product coverage. Let sit until foam breaks down and then remove using an Otis Breech-to-Muzzle(R) cleaning kit or Ripcord(R).