The PBF is a Russian gas mask that is sometimes incorrectly referred to as the GP-6 (the GP-6 is an improved version of the GP-5). The PBF takes two EO-19 filters in the cheeks of the mask, allowing the mask to weigh less than a conventional mask and have the advantage of giving easier breathing to the wearer. However the masks disadvantage is that these filters cannot be changed easily and the respirator for the face must be removed for replacing the filters.
The PBF was used by the Officers of the Soviet Army, and later by riot police and militaries of some post-Soviet states.
The unique design allows wearing a helmet much easier than having to change masks during/after combat.
It is best known for its appearance in the S.T.A.L.K.E.R. series of games, worn by numerous different characters in the game world.