Bulletproof glass. Technicians testing a pane of Sentry-Glas Plus bulletproof glass against axe blows delivered by a robot arm. The glass must be able to withstand 70 blows, each equivalent to the full force of a strike from a fully-grown man. The pane consists of a layer of plastic sandwiched between glass layers. The glass is 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 by dropping large steel balls onto it. Photographed in the Gun Testing Facility of the State of Baden- Wuttemberg in Ulm, Germany.