Jun 24, 2021 · Thank you for purchasing the HOLOSUN HE508T-GR/RD X2 Open Reflex sight. This open reflex optical sight is sized for use on either a pistol or rifle. The stream lined design, Shake Awake™ technology and our Solar Fail Safe™ dual power system combine to make it the ideal sight for small arms. Before operation, please read the User's Manual