I have used them for years, both custom and factory pre-set ones. They really work, with an accurate rifle, quality rangefinder, and BDC reticle you can do some accurate shooting. The real key is PRACTICE!!! Shooting 1 gal milk jugs at different ranges from field shooting position is the best you can do! My daughter killed a NV Mule Deer at over 600 yds. with her Burris Ballistic Plex a couple of seasons ago. I killed an buck antelope at 661 yds with my Leica ER 3.5-14 last season. They work! NJS