The 517A65 was developed to optimize the functionality of the HWS. The buttons have been moved from the back to the left side for instant access, allowing a magnifier or a back up iron sight to fit closely to the HWS body. This button position allows the user to operate the HWS function switches easier than ever before. Additionally, a portion of the front base has been raised to allow the sight to fit over standard hand guards found on many M-4 or M-16 style weapons