Call Of Duty 4 : Modern Warfare
C4 x2 is a first tier perk in Call of Duty 4: Modern Warfare that gives a player two packs of Composition-4. This perk is available at level 4, and can be combined with the perk Sonic Boom to increase the killzone radius. C4, when deployed, can be activated by tapping the use button twice. However, the farther the player is from the C4 the longer it will take for the C4 to detonate. When a player is killed, the C4 that he/she has deployed will be removed from the game once he/she respawns.