ASTM A135 is a specification for Electric Resistance Welded (ERW) steel pipe. It is commonly used in fire sprinkler systems, welding, and other construction applications. The specification includes two different types, Type E and Type S. Type E is mainly used for commercial and industrial applications, while Type S is mainly used for residential applications. ASTM A135 is available in sizes ranging from 1/2 inch (12.7 mm) to 6 inches (152.4 mm). It is also available in a variety of wall thicknesses.