This plastic unit with galvansied compentents (spindles and bearings) RoofWhirlys4Africa 240mm (325mm across the vanes) roof mounted wind turbine ventilator (also known as whirlybird or whirlybird vent) is a free-spinning roof ventilator that provides fresh air continuously (24/7) all year round! Supplied with a base plate for a steel (corrugated) roof. There is no operating cost - it uses wind and indoor heat (convection) to turn. This product is lightweight, strong and durable and highly resistant to extreme climatic conditions. An economical and effective way to assist in ventilating all types of buildings (e.g. houses, clinics, schools, offices and factories). Removes hot air in summer (to cool buildings / roof cavities). Removes excess moisture from buildings / roof cavities in winter. Fits any roof pitch from 0 to 45 degrees. This product is whisper quiet. The design including 2 sealed bearings ensures excellent performance and quick startup (dynamically balanced with 2 bearings for frictionless rotation at even the lowest wind speed). Exceptional design - straight vanes more efficient - deflect water and dust. Outstanding warranty and a unique selling point is this product is fully serviceable (after a severe hail storm etc). Spares are inexpensive and readily available. This is a tried and tested SA designed and wholly manufactured in South Africa using world standard technology and materials. Installation is quick and easy on any almost roof type as a DIY project or by a local roofing contractor (a roofing contractor can install a RoofWhirly4Africa roof vent in less than an hour). "Fit and Forget" - the roof turbine vent is maintenance free. Manufactured using superior virgin thermoplastic material designed for applications where superior impact properties and toughness are required at ambient temperatures as well as below 0 C. Used in products like industrial crates and boxes, transport containers and automotive components. Proprietary UV, colour and heat stabilisation package specification is minimum 10 years in outdoor applications in Southern Africa. This is NOT a chimney vent and cannot be used for a chimney as it is a fully plastic unit.