Little is known of the smaller variant used by Covenant troops to breach UNSC vessels, though the larger variant has been seen close-up. The charge's appearance is that of a long bulbous shape with many spikes protruding from it. It has a central control hub located at the top of the bomb. It utilizes the annihilation of matter and antimatter to create a massive explosion. Nearly 100% of the energy in the matter is released in the explosion, in contrast to the mere 7% released by a UNSC nuclear fusion warhead.
The bombs were used by the Covenant during an operation that was being conducted by the SPARTAN IIs. One of the Spartans, Solomon-069, was lured onto a Covenant Battlecruiser and subsequently killed when an anti-matter charge aboard was detonated. In another event, Cortana believed Covenant boarding parties used such a weapon to disable the UNSC Pillar of Autumn's MAC during the opening of the Battle of Installation 04.
These weapons were used during the Battle of Earth to assault Earth's Orbital Defense Platforms. The boarding parties delivered the ordnance and destroyed Athens Station and Malta Station. The bomb that was on Cairo Station was secured by John-117 and Cortana; John-117 later performed a micro-gravity maneuver to deliver the device to a Covenant Assault Carrier with shields down and a fresh 'hole' created by a pair of Longswords. The Chief entered the hole and detonated the bomb in the core resulting in the destruction of the Carrier.