The Helios FDS 355/400 Purlin Box with hinge mechanism is engineered for mounting RD roof fans and ventilation hoods on flat roofs with inclinations up to 25°. Its robust, corrosion-resistant GRP construction includes abrasion-resistant thermal and acoustic insulation for optimal durability and performance. The purlin box ensures a snow-proof base height for reliable all-weather use. Designed for easy installation and maintenance, it comes complete with mounting screws, profile rubber, and sealing components to create a tight, weather-resistant seal between the base and the fan. Ideal for professional ventilation setups on modern flat roof systems.