Precision-built SIG ASP pistols and rifles depend on quality ammunition and fuel to perform up to SIG standards. A higher-quality, cleaner gas in a superior-engineered cylinder can influence the lifetime and performance of any airgun. Investing in SIG premium cylinders is a simple way to ensure longer-lasting, SIG precision performance. Sig Sauer Prefilled 12 Gram CO2 Cylinder (40/Pack) AC-12-40