Magpul MAG1143-BLK BSL Arm Brace Black Polymer AR-Pistol Platform Made in the USA, the Magpul BSL is an AR arm brace designed to improve the single-handed employment of large-format pistols. The BSL utilizes Magpul design and engineering to offer a stabilizing accessory with a robust feature set and trusted Magpul quality. With classic Magpul aesthetics, the BSL is compatible with Mil-Spec carbine receiver extensions and employs a simplified, durable, and easy to use adjustment mechanism. An integrated QD cup and two M-LOK compatible slots provide ambidextrous sling mounting options and enable stabilizing sling tension to be applied, drastically increasing single-handed control of the firearm. With a straight-forward design and Magpul innovation, the BSL is a simple solution to improving your AR pistol.