This is an M1 .30 Carbine 30-round magazine from KCI®.
KCI magazines are a modern and budget-friendly upgrade to keep your M1 carbine shooting reliably for years to come. Crafted from blued, heat-treated steel with chrome silicon internal wire springs and a bolt hold-open follower, these 30-round M1 Carbine magazines are the classic “Banana Clips” made in South Korea. Known for good reliability, compatible with all mil-spec and most civilian carbines. Like all KCI magazines and accessories, these mags come with a lifetime warranty to ensure reliable function.