PRI flip up front sight base for .750" heavy profile barrel. The FSB uses four set screws to attach the FSB to the barrel. Comes with box and gas tube roll pin. I would like $155 shipped within the CONUS or will trade for the same PRI flip up FSB that uses two allan capscrews for attachment. Can be either for .625" light profile or .750" heavey barrel profile. The email button is the best way to contact me.