LaserMax is the originator of the guide rod laser. I have one for my Springfield XD 45 ACP and it functions flawlessly. I can't say anything negative about it and the installation is quite simple. Plus the beam is either steady or pulsating (which is easier for the eye to recognize quickly). The best part is that the laser is already sighted for the specific weapon you purchase it for (except the 1911's and revolvers). At 25 yds it is +/- 2 inches, which is more than acceptable for defensive scenarios. Unfortunately, they do not offer one for the 24/7----yet.