Green gas is tried and true, but there are plenty of situations where you might need something else. Maybe you want more kick, but can't run CO2, or you are really itching to take out your GBBR but it's freezing cold outside. It's those moments where HPA shines. The CQB Russian HPA adapter is perfect for situations where running green gas is less than ideal. With minimal work, and a little getting used to, an HPA setup for your GBB rifle or pistol can provide extremely smooth consistency, accuracy, ease of cleaning, and the opportunity to play in situations where green gas can't.