LRUs can improve maintenance operations, because they can be stocked and replaced quickly from distributed nearby on-site inventories (sometimes mobile storage), restoring the mobile systems to service, while the failed (unserviceable) LRU is undergoing complicated repair and overhaul actions in other support locations (lines).
Because of their modularity, LRUs also can contribute reducing system costs and increase quality, by centralizing development across different models of vehicles.
It is common for LRU trays to have standardized connections for rapid mounting, cooling air, power, and grounding.
Front-mounted electrical connectors are often jacks for ring-locked cannon plugs that can be removed and replaced (R&R) without tools.
There are also requirements for flammability, unwanted radio emissions, resistance to damage from fungus, static electricity, heat, pressure, humidity, condensation drips, vibration, radiation, and other environmental measurements.