The Fixer class in World War Z must choose the Masking Grenade or Supply Bag while surviving the apocalypse. A horde of zombies presents many challenges. If you know what we're up against it becomes easier to decide what we need to achieve our goals.
Ammo becomes a problem when relentless swarms overrun a position. As a Fixer, we support our team. Will they need more Firepower or Concealment? That decision is made when you figure out the playstyle you feel most comfortable with.
Masking Grenade vs Supply Bag
As a Fixer, we have two main pieces of equipment types to choose from. Go offensive with the Supply Bag by providing ammo and Explosive Rounds. Or be Defensive and help their teammates survive with the Masking Grenade.
If the zombies are eliminated then there is no need for defense. On easier levels, for inexperienced players, the ammo box may provide more benefits in comparison. Its use is straight forward. The masking effect takes some time to understand.
Starting equipment for the Fixer class is the Supply Bag. Restores 10% of primary weapon ammo for each use. Up to 4 times per bag. With a 20% chance of also getting explosive bullets. Used to resupply yourself and squad members when low on ammo.
Fixer Class can later unlock the Masking Grenade. Opening up new possibilities in World War Z. Migrating from pure offense to defense. This equipment is unique. It provides invisibility to those inside the gas. Zombies will stop pursuing you and become confused. Also giving temporary health and even becoming lethal to any zombie near the gas cloud.
Each equipment has its pros and cons. I always use grenades because we usually don't run into ammo problems. Headshots kill all regular zombies in one hit. Allowing us to speed run missions and pop smoke if we get into a tight situation.