I realize this is an old thread, but it really saved my neck. I have the newest Samsung, the UN65KS9000F. The bottom two tapped insets for the 400x400 VESA mounts were standard M8. No problem. The top two insets would not fit either a M8 or a M6 (although a M6 would turn in just a little.) Customer service was useless. It turns out in the upper holes, you need to screw in the special adapters for the Samsung on-the-wall mount (which I was not using, just a standard VESA bracket.). These adapters give you a standard M8 thread to screw into. The also make up for the difference in thickness, since the top part of the TV is much thinner than the bottom part. Unless I missed it somehow, the manual says nothing about this.