Stern Defense Mod 4 Upper Receiver 9mm 4" Barrel M-LOK Rail - 015SD4INCHMOD4MLOK4INC

Stern Defense Mod 4 upper receiver chambered in 9mm with a 4-inch 4150 Chrome Moly Steel barrel and integrated 4-inch M-LOK rail system. This pistol-caliber upper is compatible with standard AR-15 platforms and features a 1:10" twist rate. Designed as a drop-in conversion kit for AR-15 lower receivers.