When shopping for a privacy screen, or filter, for the monitor attached to your desktop PC or laptop, make sure you pick the correct size. If your monitor is not widescreen, but instead more square in shape, then you need to get the 5:4 ratio style. For widescreen monitors, the screen filter will actually be labeled as 'widescreen' and indicate the screen size, such as 21.5 inches or 24 inches. To determine the size of your screen, measure the interior viewing portion from the bottom left corner to the upper right corner, diagonally.
For a 17" standard ratio monitor, which is quite common in office environments, you should look at the 3M PF17.0 Monitor Privacy Screen. It currently retails for $54.02 on Amazon.com and that price includes free shipping. If you have a large 24 inch widescreen monitor, you might consider getting the 3M PF24.0W Widescreen Privacy Screen. It currently retails for $91.24 on Amazon and that includes free shipping. The cost is higher than the standard 17 inch model because it's just much larger.
For your laptop computer, 3M makes a screen for nearly every size monitor available. They even make privacy screen filters for netbook size computers with 8.9 and 10.1 inch screens, and those sell for around $25 on Amazon.com. Be sure to consult the manufacturer's website for information on your specific model laptop or netbook in order to make sure you get the appropriate screen size.
To install these filters, simply snap them into place over your screen. As an added bonus, they also add an extra layer of protection to the LCD panel, which is nice for people who like to touch the screen. On the downside, these do somewhat darken the screen and may require you to turn up the brightness and contrast in order to see more clearly.
(Image credits: 3M and Amazon.com)