From The TimeSplitters Wiki

Basic information

Body Armor (Armour) is used as a secondary health bar, thus extending your overall lifespan during the course of the mode your playing in.

Forms

In the TS games, Body Armor can take many different appearences, depending on what Timezone it's in.

Types

Just like Health Packs, Body Armor comes in two types:

• Small: Recovers a varied amount of armor, sometimes a lot, sometimes not very much.
• Large: Restores your armor bar to full.