Very effective - EOTech 517 A65 Holographic Weapon Sight (HWS) Buttons On Left Side w/ Raised 7mm Base (517.A65/1) for M4 & M16

EOTech's 517 holographic weapon sight is easy to mount and sight in. Once done, it needs no resetting if removed from the weapon via quick release. The 517 itself has excellent eye relief, however, be aware that when combined with the EOTech's 3x Magnifier, eye relief is very shallow. That being said, shooting with the magnifier almost feels like you're cheating. Amazing accuracy and ease of use. Shooting buddies can't believe the groups I can shoot with this thing.
Pros: Quick Target Acquisition
Cons: Cost/Weight

This review was written in the old system and had content requirements that are different than reviews written today.