This is a Gemtech Thread Adapter known as the 22 QDA chambered in 22 LR, model 12202.
The 22-QDA four lug muzzle device is threaded 1/2-28 to mount on all standard rimfire threaded barrels for maximum compatibility.
Features:
The 22-QDA four lug muzzle device is threaded ½-28 to mount on all standard rimfire threaded barrels for maximum compatibility.