The Midwest Industries upper receiver rod is the ultimate tool for barrel nut installation or removal and is excellent for removing stubborn/seized barrel nuts without damaging upper. This receiver rod is also designed for muzzle device installation and will not damage the index pin. This receiver rod can also be installed horizontally or vertically in a bench vise and works with any standard M4/M16 barrel extension. Please note that this is NOT COMPATIBLE with 9mm and rimfire barrels and is also NOT COMPATIBLE with DPMS G2 308.