These heavy drilling self-drilling screws are a staple of any construction drill screw program. Able to drill steel up to 1/2" thick. Featuring TanCor Corrosion Resistant Coating, which provides 1,000 hours of salt spray protection. Self-drilling screws are heat treated in strict accordance with SAE J78 industry standard. It is NOT recommended to use these drill screws in critical applications where dissimilar metals (aluminum) and exposure to moisture are involved. These heavy drilling self-drilling screws are proudly made in the USA, steel is melted & poured in the USA.