The Helios Fans ZRL 125 includes a telescopic duct (DN 125) adjustable from 260 to 500 mm, combined with a soffit channel made from EPP, rated to fire protection class B1. The kit is supplied with two plaster covers for internal and external use to protect the duct during the shell construction phase. Its flexible design allows for installation on either side of the window without requiring modifications. For optimal performance and compliance, the soffit element must be fully overinsulated and is not suitable for wall constructions with insulation thicknesses of 100 mm or less.