The Echo AK-47 Trigger is a drop in trigger for the AK-47 Platform. The Echo AK-47 Trigger is a response trigger that allows the shooter to fire a round on the pull and also on the release of the trigger. The Echo AK-47 Encompasses the same patented trigger lock technology as the Echo AR-II. The trigger lock keeps the operator from running the firearm. The Echo AK-47 like the Echo AR-II has multiple patents from multiple companies. The Echo Trigger allows the shooter to select from 3 different settings: Safe Mode: Firearm will not fire. Semi-Automatic Mode: Firearm fires when trigger is pulled. Echo Mode: Firearm fires when trigger is pulled and also when trigger is released. The Echo AK Trigger is designed to work with stamped AK's. As a general rule milled AK's should also work as long as you are willing to work with the mode selector plate and the trigger blade in some cases. We have yet to find a gun that it won't fit in. It's the parts outside of the receiver that generally causes issues. However, due to the inconsistent nature that many AK style rifles/pistols have been and continue to be produced, individual results may vary. Below are some milled AK's tested to be compatible: Molot-Oruzhie LTD - Vepr Rak Com Bloc Childers Guns- CG1 Century Arms - AK63DS Arsenal - SAM7R Arsenal - SAM7SF Interarms - AKM47 Riley Defense Inc. / Morrissey Inc, - AAM-74 CAI (Century Arms Int) - N-PAP M70 CAI (Century Arms Int) - WASR-10