About Fostech Fostech is a family owned company based in Southern Indiana. Fostech Inc makes AR-15's, 12 Gauge Shotguns in AR style, binary triggers for both the AR and AK platforms, as well as many AR parts. All Fostech products are proudly made in the United States. The Echo AR-II Trigger is a groundbreaking drop-in design that is approved by the ATF. The Echo AR-II trigger does not come with a bolt carrier. You will need a full auto bolt carrier in your firearm for the Echo AR-II to function. The Echo AR-II is designed to function in the AR-15 Platform. If you have any questions in regards to if you have a full-auto carrier, please visit echoquestions.com.