AimShot 338 Lapua Magnum Arbor for use with any of the AimShot 223 laser bore sights. This arbor will fit over any of the AimShot 223 laser bore sights and allow you to bore sight any 338 Lapua Magnum rifles. We recommend using the MBS223 modular laser bore sight as it allows use in closed chambers when using the smaller batteries, or in most rifles with the external AAA battery pack (20+ hours of battery life!).