The Steel Window Myth Explained
There are many different profiles, which are all supplied by one supplier, a company called Montanstahl. They hot roll the steel to form the profiles used by window manufacturers. You will see the likes of W20, W30, W40, W40, W50TB etc used in the UK. (for architects only this bit: If you specify a Shueco aluminium window system, Shueco will ask one of their fabricators to manufacture and install it for them, as Shueco are the aluminium profile system producer. Montanstahl are the producer of the steel window profile systems.)