Corrugated Aluminum Pipe (CAP) is made of pure aluminum. Aluminum pipe is preferred in some locations where its greater corrosion resistance is an advantage. It is fabricated in two corrugations that are identical to those of Corrugated Steel Pipe (CSP). These helical corrugations are 2 2/3" x 1/2" (sizes 12" through 60") and 3" x 1" (available in diameters from 30" to 120"). Aluminum pipe is also offered in pipe-arch sizes equivalent to 15" to 96" round pipe.