A lightweight, bendable, and extendable aluminium duct. It is also available with pre-mounted end pieces featuring a female (muff) connection as standard, referred to as “Compact MM, and can alternatively be supplied with a male (nipple) connection. It is used as a ventilation duct for various applications including industrial facilities and small residential buildings. Delivered in a compressed state, it can be extended to four times its compressed length. It consists of a single layer of aluminum strip that is corrugated and seamed together. The bending radius is calculated at 0.5–1 × the diameter. These ducts are available in diameters Ø80 mm–Ø315 mm and can be produced in many different lengths, including custom dimensions. They are classified as non-combustible in material class A1 and meet tightness class C.