Most of our timber core layers are made of hardwood cross plywood, because this is the most sound structure of engineered boards, is been broadly used by most European manufactures. Our core layer plywood are made of 7-11 layers pure birch, eucalyptus and birch, or eucalyptus and poplar, depends on what EURO oak collection the products belong to. With the solid timber top layer, we guarantee you sand the floor back twice with 4mm top layer and 4 times with 6mm top layer in future.