There are many benefits to carrying a spare mag in the field. You can shoot for longer periods of time and with less interruptions. Instead of fiddling with a malfunctioning or broken mag, simply insert a pre-filled new one into your airgun. The ASG X9 16rd BB Pistol Magazine is designed for the ASG X9 CO2 BB Pistol Blowback. The mag holds 16 rounds of 4.5mm steel BBs.