Reactive armour is a type of vehicle armour that reacts in some way to the impact of a weapon to reduce the damage done to the vehicle being protected. It is most effective in protecting against shaped charges and specially hardened kinetic energy penetrators. The most common type is "explosive reactive armour" (ERA), but variants include "self-limiting explosive reactive armour" (SLERA), "non-energetic reactive armour" (NERA), "non-explosive reactive armour" (NxRA), and electric reactive armour. NERA and NxRA modules can withstand multiple hits, unlike ERA and SLERA, but a second hit in exactly the same location may potentially penetrate any of those.