Modern day armored vests were originally known as "flak jackets", and were used by bomber crews to protect against high-caliber proximity-detonated anti-aircraft shells (flak). After research during the Vietnam war showed that 2/3 of casualties were from fragmentation, not bullets, body armor saw a proper return to the frontlines.
— Battlelog description
The solo specialization is unlocked at rank 8, while the squad specialization is unlocked at rank 29.
FLAK is a specialization featured in Battlefield 4. It decreases damage from explosions by 15%. It is a part of numerous Upgrade Paths. As in Battlefield 3, the specialization does not protect against direct hits from explosives.
- Defensive - Third Specialization
- Grenadier - Fourth Specialization
- Mechanic - Second Specialization
- Anti-Tank - Fourth Specialization
— In-Game Description
Flak is a Specialization featured in Battlefield 1 for all kits. Introduced as part of the In the Name of the Tsar expansion, it was added to the Community Test Environment in August 2017. The specialization reduces damage from all incoming explosives by 10%.