The Double Star Strongarm Pistol Brace is compatible with any JMAC Customs Arm Bar with the AB-BA Brace Adapter. 

From the Manufacturer

When firing a PDW-style pistol, control is imperative. DoubleStar introduces the new Strongarm™ Pistol Brace. Machined from billet aluminum, the Strongarm™ provides a rock-solid plate that fits securely on most AR-style pistol buffer tubes with two clamp screws. For added control, the Strongarm™ also comes with a velcro strap to secure the pistol to your forearm for easy one-handed shooting.