Not sure if this was a 'challenge' to what I posted or not .. . The 3600 cards aren't certified by Lexar for the 1DXII; the 3500 cards are . I did use a 3600 for a few assignments . I can't say what the cause for the loss of 2 -3 images was specifically, but it's only happened with the 3600 under similar shooting conditions with the 3500 and the included SansDisk . I also had a discussion w/ Lensrental re the 3400/3500/3600 compatibility. Their view - the 3400s didn't work at all, 3600s aren't 'certified', so if one dos Lexar, go 3500 . That being said , I did get 25K + images using the 3600 .. it's a YMMV situation . Not sure what one gets from a 3600 versus a 3500 , as their specs and retail price are very close , so why not be safe ?