Bulletproof glass. Technician examining a pane of Sentry-Glas Plus bulletproof glass onto which a steel ball was dropped during testing. To meet safety requirements, the glass must be able to resist 3 impacts by this 5 kg ball from a height of 9 metres. The pane consists of a layer of plastic sandwiched between glass layers. The plastic makes the glass 100 times more rigid than previous types of bulletproof glass. Such glass, which is used in military vehicles, armoured limousines, banks and museums, is also tested using bullets and blows from weapons like axes. Photographed in the Gun Testing Facility of the State of Baden-Wuttemberg in Ulm, Germany.