Hey there. . . I usually just lurk around here, but I know a little bit about this one. I have some of these on my site; both mechanical and laser. I have one of each (mechanical one by Simmons and laser by LaserLyte) for around $45, and another that is around $60. All of them work as well as any that I have used.
Everyone else here is correct though; the boresighters are just to get you in the neighborhood. Don't go spend a lot of $$ on one; you likely won't get the additional performance to justify the extra money spent.
Although I do carry a couple that are more expensive (you have to purchase the base unit and then any arbors for additional calibers that you may wish to sight, which can get a bit pricey), I wouldn't recommend them over the basic ones. An inexpensive one can get you on paper; from there you need to sight your weapon from a bench for good results. Regards, Lance
If you are interested, here are the links (please excuse the lack of organization; we are still working on it!