Our STT-15 lower receiver was born out of necessity and a desire to have a true ambidextrous AR-15 M4 platform. Allowing it to accommodate all shooters without the need to add countless costly add-ons. Whether you are a right- or left-handed shooter, or forced to shoot with your off hand, the STT-15 has you covered! STT-15 is designed specifically for situations in which there's no room for error and you must use your rifle to take that shot!