A sealed beam lamp unit is a single hermetically sealed assembly where the reflector, lens, and light source cannot be separated without destroying the unit. This integrated construction is the defining classification criterion — automotive lighting assemblies where the bulb is replaceable separately from the housing are classified differently, typically under lighting or signaling equipment headings.

Sealed beam headlamp units intended for use on motor vehicles sold in the US must comply with FMVSS (Federal Motor Vehicle Safety Standards) administered by NHTSA. Importers of aftermarket sealed beam units should confirm compliance with applicable photometric and dimensional standards, as non-compliant lighting equipment may be subject to detention or refusal at the port of entry.