WD-40 Specialist Penetrant contains a proprietary blend of ingredients that work fast to free rusted bolts and other stuck parts. The capillary action penetrates into tight crevices, threads, and seams to break the bonds that hold stuck parts together. It helps prevent rust and corrosion from re-forming and leaves behind a lubricating layer. The professional-grade formula is low odor, working effectively without the harsh, lingering scents of other penetrating oils. Use Penetrant on nuts, bolts, pipe threads and rusted things that are stuck and won't move! It is safe to use on most common application surfaces, including most metals, plastics, and rubbers when used as directed. If unsure, test on a small area first. 13.3oz size is exclusive to Amazon and gets more done.