From Halopedia, the Halo wiki
ComL is a type of high explosive mixture used by the United Nations Space Command in the M9 High-Explosive Dual-Purpose Grenade. It is a generally stable mixture which is extremely destructive when primed and detonated. Only 0.19 kg of ComL is used in one grenade. ComL is relatively inexpensive to use and is effective at propelling the shrapnel from the grenade.
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