Thread Protector 1/2x28 Knurled Silver Color AR 15 10 223 556 300 AAC Thread Protector 1/2x28 Precision Manufactured, CNC turned to ensure the highest quality knurled on the OD for a positive grip for easy on and off Machined from 7071 AIRCRAFT GRADE aluminum Hard Coat Anodized FITS ANY 1/2X28 THREAD