Simplify the following text for a Grade 9 native English-speaking person.
Original: These banknotes are made from the polymer biaxially-oriented polypropylene ( BOPP ) which greatly enhances durability of the banknotes . Polymer banknotes also incorporate many security features not available to paper banknotes , making counterfeiting much more difficult .
Simplified: Seven countries are now fully using polymer banknotes on all of their banknotes instead of paper .