Having just purchased a D800 I needed faster cards. I picked up the 32gb Sandisk Extreme CF and SD cards. I tried them with both cameras and they work fine. The D300s however does not take full advantage of 60mb/s of the CF cards. Fastest supported speeds based on research I did on Nikonians suggests speeds of 30 mb/s are fully supported and my testing agrees with that assessment. The D300s is a great camera btw. Still love it after several years and newer/better camera's!