Biathlon Targets are self-indicating, they flip from black to white when hit, giving the athlete as well as spectators instant visual feedback for each shot fired. The biathlon target range shooting distance is 50 metres (160 ft). There are five circular targets to be hit in each shooting round. When shooting in the prone position the target diameter is 45 millimetres (1.8 in); when shooting in the standing position the target diameter is 115 millimetres (4.5 in). The change in target diameter is not visible to the spectator or athlete with the naked eye. Young athletes start with a shooting rest in the prone position, then progress to shooting with no rest in the prone position. The typical age to start shooting from a standing position is 14 years old or older. Standing position requires greater physical strength and size.