The KILO BDX rangefinders use Applied Ballistics and Bluetooth® to illuminate the exact holdover dot in SIERRA3BDX riflescopes. For the most accurate and ethical shot, just Connect The Dot™. - DOWNLOAD: Download the app - SYNC: Sync the app with your rangefinder - BOND: Use the app to bond the rangefinder with the riflescope - RANGE: Press the RANGE button to measure the distance of your target - POWER SELECTOR RING: When the SIERRA3BDX riflescope is actively paired with a KILO BDX rangefinder, the blue LED on the power selector ring will be illuminated solid blue. This Blue LED will flash quickly 8X for one second whenever the riflescope has received a new holdover reticle update from the rangefinder. The BDX system works out to 800 yards with 1 MOA of accuracy - CONNECT THE DOT™: It’s time for hunting. Once the riflescope is turned on, range the target and the new hold is lit up out to 800 yards