Fostech Echo Sport AR-15 Binary Trigger Black. These Rifle Triggers from the innovators at Fostech feature a safe mode built in that prevents your rifle from firing unexpectedly. With a semi-automatic mode the Fostech AR-15 Trigger only fires when you pull the trigger. Expertly designed the Fostech Drop-In Rifle Trigger runs smoothly on your favorite AR platform. Specifications for Fostech Echo Sport AR-15 Binary Trigger: Manufacturer: Fostech Color: Black Gun Model: AR-15 Gun Type: Rifle Condition: New Features of Fostech Echo Sport AR-15 Binary Trigger: 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 Sport trigger does not come with a bolt carrier. You will need a full auto bolt carrier in your firearm for the Echo Sport to function. Package Contents: Fostech Echo Sport AR-15 Binary Trigger What firearm models does the manufacturer say Fostech Echo Sport AR-15 Binary Trigger is compatible with? The manufacturer says that Fostech Echo Sport AR-15 Binary Trigger is compatible with AR-15Fostech 4140: Echo Sport AR-15 Binary Trigger Black