iStrelok is a ballistic trajectory calculator. - 874 reticles supported! Full list see here: http://istrelok.borisov.mobi - You can see holdovers on your reticle and scale holdovers to any magnification (if reticle is located in second focal plane). - Trajectory calibration ("Truing") feature. - abitity to change target type and select from: Round target (you can change diameter), Old IPSC Target, IPSC Target, IPSC Universal Target, IPSC Mini Target, IPSC A4 Target, IPSC A Target, Target number 4. And animals targets: Fox, Coyote, Wild Boar, Aoudad, Crow, Moose, Elk, Whitetail Deer, Rabbit, Rat, Pingeon, Marmot. - ability to input current altitude from internal GPS sensor - supports WeatherFlow WINDmeter (not WEATHERmeter) - iPhone internal barometer support Small, handy and accurate. Field-proven accuracy since 2001. Supports imperial units (yards, feet, inches, etc).