This includes AKs, Valmets, Galils, and MAK 90s, just to name a few.
Installation takes less than a minute and can be done without any special tools.
What makes the kalashnikov action so reliable, is also what causes its inevitable downfall, the violent manner in which it works. Each time you fire your rifle the gas system propels the bolt carrier to the rear very violently, which generates a shock wave that is absorbed by the metal receiver. After a period of time, this repeated pounding causes the action itself to lose its structural integrity. The most notable side effect of this is the difficulty one has in controlling the weapon during rapid fire. They work so well that many people believe they should be installed in all guns by their manufacturers.