So I snagged a Samsung 70 inch NU6070 grreat.
I take down our 55 inch that's already mounted (the mount is universal VESA and handles up to 110 lbs, the new TV is only 58 lbs) to put the brackets on the back of the TV. Wrong screw size.
I look in the book. It says there I need 49 mm, M8 1.25...