Extensions come in pairs and are mounted on the sides of the shoulders. They are miscellaneous, usually non-offensive devices, and can be anything from extra boosters to stealth devices.
- Extra boosters (with various functions)
- Anti-missile systems
- Relation missiles (extra missiles that fire simultaneously with missile launchers)
- Shoulder energy shields
- Emergency heat sinks (rapidly cools an AC)
- Emergency energy units (rapidly recharges energy)
- Enemy Radar Jamming systems
In Armored Core 3, several emergency energy units were sold - these were usually 3 uses, and would quickly refill the energy of an AC in about 5 seconds. Emergency heat sinks were also introduced that allowed a quick cooling burst to bleed off potentially damaging heat if an AC got too hot. In Armored Core 2, additional booster and relation missiles become available but in "Armored Core: Nexus" the radar jamming equipment was removed along with the radiator and ECM equipment.