Laminated glass can be made to resist extreme wind and airborne flying debris that occurs during a cyclone. In such situations the glass must withstand penetration from a 4kg, 100x50mm timber plank travelling at 15m/s or more. To do this the interlayer must be strong and thick (typically 14mm). The glass is usually made up of two 5mm thick glass sheets bonded together with a 3.8mm PVB interlayer. Sometimes the glass is even thicker as the wind pressures are very high in cyclone conditions.