There are very high technological requirements set for bottle caps: On the one hand they should seal the bottle and reliably protect the product; and on the other hand, the consumer must be able to easily open the bottle and if desired, reseal it. And, of course, the cap must not impair the bottled beverage. Therefore, special sealing materials are required; they must be effective sealers, wear-resistant, tasteless and be easy to use. To fulfil all these criteria, an auxiliary material is added to the sealing materials and as with all the packaging products, we set the strictest quality standards, and there are no potentially hazardous materials are used in the caps used by Gerolsteiner.