The KWA 1911 MK-IV Series 21 Round Magazine is a high-capacity, heavy-duty metal airsoft magazine designed for the KWA 1911 Series NS2 Gas Blowback (GBB) pistols. 
 
Key Features & Compatibility
Compatibility: Designed for KWA 1911 MK I-IV Series and new M1911A1 airsoft GBB pistols utilizing the NS2 gas system. When this magazine was introduced, KWA noted it required installing new parts (included with early runs of the magazine) like a new slide catch and magazine release to accommodate the increased capacity in older models.
Capacity: Holds 21 rounds.
Construction: Features a heavy-duty metal construction for durability.
Performance: Utilizes a high-tension steel spring for improved feeding consistency and reliable gas seal.