The laser bore light in green reticle is a useful tool to zero an optic without firing an actual round of ammo . I sighted it at 17 yards in my house on a Holosun SCS for an HK VP 9 . First shots were center mas but a bit low left . A couple of minor adjustments and then dead on . So, the tool works well enough to get your optic close to zero . Only used 5 rounds to finish off the adjustments .