After different, longer test series (weathering, solar radiation, temperature, reflection, etc.) with different materials (stainless steel, high performance plastic, different anodized surfaces, etc.) we decided for the material aluminium with a black anodized surface. This material has led to the best results when using the QR badges. Since we want to offer the best possible service to our customers, we sell our product exclusively made of high-quality, black anodized aluminium.