This Low profile micro gas block is constructed of All Steel Construction. The Low profile Micro gas block replaces the existing A2 front sight and is sleek and small to allow a longer rail to be placed over. Can be used when installing a Mid Length Specter Length or Rifle Length hand guard to a shorter length gas system barrel. It is compatibe with .308 & 5.56/.223 Bull Barrel with a .936 diameter barrel. Roll pin & set screws are included. No modification to your barrel is require