Of all the bombs dropped on Britain by the German air force of WWII, these small devices were the most numerous type. The Thermite incendiary material burned at extremely high temperature, setting fire to any combustible material in its proximity.
This example is the standard B1 EZ type, which weighed 1kg. There was also a 2kg variant which incorporated a small high explosive anti-handling charge.
All over Britain, these bombs caused thousands of fires and were even responsible for the largest conflagration since the Great Fire of London.