A Power Limiter, otherwise known simply as a "limiter", is a device manufactured by the Umbrella Corporation to prevent the uncontrollable mutations a Tyrant may experience, which prevent the B.O.W.s from being properly controlled.
They are specially designed coats worn primarily by T-103 Tyrants. They are made of a strong, bullet-resistant fabric that makes most Tyrants nigh invulnerable, except for their exposed heads. Once the coat is destroyed, more often than not a Tyrant will immediately mutate into a Super Tyrant.
Tyrants outside of the T-103 series do not wear these coats but are still capable of resisting firepower, however the drawback is the shorter lifespan and lack of mutation.
The Nemesis-T_Type, which had its origins in the T-103, also possessed a Power Limiter in its own coat, which was destroyed in the fire of the cable car wreckage, after retreating from an attack by Jill.
Tyrants encountered by Leon Scott Kennedy during the East Slavic Civil War in Eastern Slav Republic were identical to the T-103 Series having a power limiter coat and identical appearance, but were exceptionally larger and higher in build and lacked an exposed heart. After the power limiter was damaged, it caused them to mutate, they were noticeably much more powerful than any Tyrant encountered before due to their large build, they were taken out later by missile fired at them by special forces pilots.