The Trijicon TA01 four power telescope, with its BDC reticle, makes a perfect match for this custom flat top AR-15 HBAR (Heavy BARrel). The TA01 is mounted to the receiver rail using the TA51 mount. The scope has separate aiming points for 100, 200, 300, 400, 500, 600, 700, and 800 meters, plus tritium illumination that makes the reticle glow red in low light. Thank you, Matt, for the loaner rifle.