Increasing demands on cold strip quality place a growing requirement on good flatness. Traditional flatness measurement systems are contact based systems, which can cause scratching of the strip surface, and require extensive maintenance work. The SI-FLAT method developed by Siemens uses a contactless measuring principle. It minimizes the risk of scratches and reduces operating and maintenance costs. The system is less sensitive to tension variations and mechanical misalignments, and provides best resolution at the strip edges because of narrow sensor stacking and integrated strip edge detection. SI-FLAT is proven for steel, stainless steel, non-ferrous material and aluminium.