Thread Protector fits AR15 HBAR Contour 1/2 x 28 Stainless- Protect and beautify your HBAR muzzle threads with this beautiful knurled stainless thread protector. Standard 1/2 x 28 thread with a length of 5/8th inch and .740" diameter, it fits all EABCO and Shaw 1/2x28 HBAR barrels perfectly.