LCD monitors and screens that are 12 inches to 22.9 inches diagonal are classified in the small to medium range. These screens fall into the weight category of up to 30.8 pounds. The VESA requirements for screw separation distances for mounts intended for small to medium screens are 75 by 75 millimeters or 100 by 100 millimeters.
LCD monitors and flat screens that are between 23 inches and 30.9 inches diagonally are classified as large screens. Screens in this category should be no heavier than 50 pounds. The VESA screw separation requirements for large screen wall mounts is 200 millimeters by 100 millimeters and 200 millimeters by 200 millimeters.
Screens that are 31 inches to 90 inches diagonally and are between 50 to 250 lbs have various hole patterns in 200 millimeter increments. These increments range from 400 millimeters by 200 millimeters to 800 millimeters by 400 millimeters.