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A lightweight, non-ballistic protective helmet designed to guard against blunt impacts, falls, and flying debris. Unlike heavy combat helmets, they do not stop bullets or fragments. They are meant to reduce pain from impacts, and reduce the likelihood of concussions; the heavy weight and ridgid frames of aramid helmets or steel helmets can actually worsen the user's risk of concussions and neck injuries.
Mostly obsolete, bump helmets were historically used by paratroopers, special forces soldiers (in particular the Navy Seals (usa), and SWAT/police tactical units. They are still widely used by many tank crewmembers, particularly in the former Soviet Union, who do not generally face ballistic or fragmentary threats.
This tag implicates helmet (learn more).