I have KNS gas pistons on several AK's and love them. I have two complaints, but I might just call them product improvement ideas. First, the included roll pins need to be longer. They're only long enough to catch on one side of the piston. Second, when installed on some rifles, there is a gap between where the factory piston leaves off and where the KNS piston starts. In other words, a factory piston can cause the rifle to eject cases too far while the KNS piston on the same rifle in the fully closed doesn't allow enough gas to reliably cycle the action. I've had this happen on a couple of AK's, but it doesn't happen on most. I can't figure out why, but it is what it is.