Crosman Semi-Auto Co2 Magazine 

A spare drop-down magazine that holds two CO2 cartridges and 28 rounds of steel BBs for rapid-fire action 

Compatible with most CO2 cartridges and 4.5 BB 

AK1 Spare Magazine 

Drop-down style with 28-round BB capacity 

Holds 2 x 12-gram Co2 cartridges