When considering a monitor's size, be aware that its size is not the same as its viewable or usable area. Manufacturers provide the viewable screen sizes, in addition to the CRT sizes, of their monitors. Since the picture tube is inside a plastic casing, the viewable screen size is smaller than the CRT or monitor size. Larger monitors require greater viewing distance. The smaller the distance between dots the better the image.
Dot pitch is measured in millimeters.
For example a .28mm dot pitch will produce a sharper image than a .39mm dot pitch. Most monitors come with dot pitches of .25 mm to .28 mm. A shadow mask tube is less expensive to produce and more commonly used in the market. They offer displays with more precision for word processing and spreadsheet applications. Aperture grille monitors are more expensive and provide better graphics with saturated colors and brightness, which makes them ideal for desktop publishing and design work.