Universal pipe for the construction of exhaust systems. Made of acid-resistant steel. The diameter given in the name is measured on the outside of the pipe, wall thickness: 1.5mm. The pipes are also available: Stainless steel elbows Slip-on stainless pipes Universal pipe for the construction of exhaust systems. Made of acid-resistant steel. The diameter given in the name is measured on the outside of the pipe, wall thickness: 1.5 mm.