The SPC-12 is a standard 12-gram compressed CO2 cartridge used as a propellant source for pneumatic weapon platforms across multiple manufacturers. The cartridge is a simple, unregulated consumable — a small steel cylinder containing liquid CO2 under pressure, with a pierceable brass seal that the weapon's action punctures to release gas into the firing chamber.

The SPC-12 is not proprietary to any weapons manufacturer and is produced by dozens of industrial suppliers for applications ranging from beverage carbonation to fire suppression. Its widespread availability and low cost make it the default propellant for weapons designed to operate outside conventional ammunition supply chains — platforms like the NDP-4 'Stutter' and PSP-2 'Gravel' that prioritize concealability and supply chain anonymity over raw performance.

Each 12g cartridge provides approximately 18 pneumatic discharges at standard pressure, though this varies by weapon platform and ambient temperature. Cold environments reduce cartridge pressure and per-shot velocity, while hot environments increase both — a variable that experienced operators account for but that novice users frequently overlook. The cartridge's steel housing makes it the only component of many pneumatic weapon systems that triggers metal detectors, leading to a black market in polymer-bodied CO2 cartridges that sacrifice some pressure containment for complete scanner invisibility.