ALG Defense AK Recoil Spring Chrome Silicon Ste. The 2 to 3 dead coils in the center change the natural frequency of the spring which prevents harmonics from damaging the spring and reducing its free length. Specifications for ALG Defense AK Recoil Spring: Manufacturer: ALG Defense Color: Steel Gun Model: AK-74 AK-47 Additional Features: 3 Centered Dead Coils Fabric/Material: Chrome Silicon Steel Package Contents: ALG Defense AK Recoil Spring What firearm models does the manufacturer say ALG Defense AK Recoil Spring is compatible with? The manufacturer says that ALG Defense AK Recoil Spring is compatible with AK-47 AK-74ALG Defense 04-231-F: AK Recoil Spring Chrome Silicon Ste