Knurled knobs GN 676 are made of blue plastic granulate that is FDA compliant as per FDA CFR.21 and EU 10/2011 as well as visually detectable or metal detectable.

The blue color is especially easy to see with the human eye and is also easy to detect with optical monitoring systems. This allows monitoring of the production process, such as in food production, so that the process can be interrupted if foreign bodies are detected.

The plastic of type MDB also contains metal detectable additives. Metal detectors will be triggered by this material as of a particle volume of about 0.125 cm³ meaning that even hidden plastic chips can be detected.