Spiral mandrel dies have significant advantages over other systems for the production of multi-layer pipes. In fact, some product developments have only really become possible as a result of this concept. Multi-layer pipes can be produced not only by the coextrusion technique, but also by sheathing with crosshead dies. Here, too, spiral mandrel dies have certain advantages. This article deals with various principles for designing spiral mandrel dies, reporting on systems that have been used in practice and on the experiences gained with them.