The main bomber force, called "Plate Rack", took off shortly after the Pathfinders. This group of 254 Lancasters carried 500 tons of high explosives and 375 tons of incendiaries ("fire bombs"). There were 200,000 incendiaries in all, with the high-explosive bombs ranging in weight from —the two-ton "cookies", also known as "blockbusters", because they could destroy an entire large building or street. The high explosives were intended to rupture water mains and blow off roofs, doors, and windows to create an air flow to feed the fires caused by the incendiaries that followed.