Specialist for years of the production of Cristal paper Grünperga commercializes raw materials for the envelope windows. In the past few months the basis weights used by this industry have trended downward: previously used 35 g / m² their quality Super Klar has been the subject of an approval procedure by the German post office in order to ensure the compatibility of 32 gsm with high-speed reading machines.

The results published on April 25th, 2013 confirmed that Grünperga’s Super Klar 32 gsm is officially approved by Deutsche Post under the certificate number: 3400S100422.