Otis O12-GP General Purpose Blend For all your firearm cleaning needs, Otis offers a general purpose blend. The O12-GP® General Purpose Blend removes carbon, copper and lead. This unique cleaner is biodegradable with no harsh odor and also acts as a rust preventative. Removes stubborn carbon, copper, and lead fouling with ease. Prevents rust and corrosion for long-lasting barrel protection. Safe on all gun metals. Safe for the environment – biodegradable with no harsh odor.