YZ-200 traces its root back to American CBU-100 cluster bomb. The M114 was used in the M33 cluster bomb. RBK-500 is a Russian 500 kg cluster bomb. It could therefore be classified as a cluster bomb. Ingram acknowledged using more 2000 cluster bomb projectiles on Basra. This cluster bomb is no longer in production. The 1999 Elistanzhi cluster bomb attack against civilians. The E61 anthrax bomblet was an American biological sub-munition for the E133 cluster bomb. The M33 cluster bomb was never used in battle. This model approximates the behavior of military grenades, and some cluster bomb submunitions. NPO Bazalt subsidiary of Russian company Techmash is developing a glide cluster bomb PBK-500U Drel. The air-to-surface variety of this kind of munition is better known as a cluster bomb. A single cluster bomb produces a total of more than two hundred thousand fragments. The anti-tank cluster bomb is an air-launched, conventional free-fall weapon. The Israeli Defense company Israel Military Industries also manufactures the more up-to-date M-85 cluster bomb.