The Fostech Echo AR-II trigger (brand part no. FOS4150) gives AR-15 owners a selectable trigger with three distinct settings: Safe, where the firearm will not fire; Semi-Automatic, where the firearm fires each time the trigger is pulled; and Echo Mode, where the firearm fires both when the trigger is pulled and again when it’s released. Safety is built into the Echo Mode design, so if the shooter needs to abort mid-cycle, moving the selector to Safe stops a second round from firing on release. The trigger carries a patented design that has received ATF approval (Patent No. US 8820211 B1), with additional patented technology licensed through Franklin Armory (U.S. Patent Nos. 9952012 and 9952013) and HIPERFIRE, delivering a light, clean, crisp pull in Semi-Automatic mode alongside reliable function in Echo Mode.

Key Specifications

• Offers three selectable modes: Safe, Semi-Automatic, and Echo Mode.
• In Echo Mode, the firearm fires on both trigger pull and trigger release.
• Includes a safety design that stops a second round from firing on release once switched to Safe.
• Carries a patented design with ATF approval (Patent No. US 8820211 B1).
• Incorporates technology licensed through Franklin Armory (U.S. Patent Nos. 9952012 and 9952013).
• Incorporates technology licensed through HIPERFIRE.
• Delivers a light, clean, crisp pull in Semi-Automatic mode.
• Built for the AR-15 platform.

Frequently Asked Questions

What happens if I switch to Safe mid-cycle in Echo Mode? The firearm will not fire a second round on release once the selector is moved to Safe.

Is this trigger ATF approved? Yes, it carries a patented design that has received ATF approval.

What does Semi-Automatic mode do? The firearm fires once each time the trigger is pulled, just like a standard AR-15 trigger.

Buy the Fostech Echo AR-II Trigger

Upgrade your AR-15 with a patented, ATF-approved Fostech trigger. Order it from our FosTech Outdoors lineup, part of our AR triggers selection, and get it shipped fast from our Lubbock, Texas gun shop.