I put the Heavy Duplex on my Knight Disc about 4 years ago...Used it one year and sent my VX-II off my Ruger .243 and had it put on it as well...I like it...the standard duplex seems a little fine to me, especially during low light conditions...Best I can tell the crosshair covers about 3/4 inch at 100 yards...So it works well on a deer rifle....I believe it cost $80 for Leupold to change....Good Luck