The E120 was a spherical bomblet with a diameter of 11.4 centimeters. It was designed to hold 0.1 kilograms of liquid biological agent. Much like the M139 bomblet, the E120 had exterior "vanes". However, the vanes' function on the E120 was to cause the bomblet to rotate as it fell, thus shattering and rolling around upon impact while spraying the agent from a nozzle.