Frag x3

Frag x3 is a first tier perk in Call of Duty 4: Modern Warfare that gives a player three frag grenades. When combined with the second tier perk Sonic Boom, the frag grenades' killzone radius will increase significantly.

Multiplayer Tactics
It is the most commonly used first tier perk. Elitist players look up on those who use Frag x3 due to the possibility of players randomly throwing (known as grenade mortaring or 'nade spamming) the extra grenades to get kills. The perk is generally only used by "assault" classes.