Wytwórnia Broni Jacek Popiński (WBP)
ALG AK recoil spring is a one of a kind design, it is manufactured from chrome silicon steel resist impact shock and relaxation. 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.
Great upgrade or replacement.
I got one of these to replace the recoil springs in my Md. 63 build, and hoo boy if it feels more like an appropriate, factory-fresh recoil spring and not an actual worn-down, military surplus one.