17" to 24"

A privacy filter darkens the screen to anyone looking from an angle, so a colleague at the next desk or a passenger beside you sees black rather than your work. It is standard practice for finance, HR, healthcare and legal work, and anywhere personal data is on screen in a shared space.

Measuring is where mistakes happen. The stated size is the screen’s diagonal, and it must be paired with the right aspect ratio — a 24in 16:9 filter and a 24in 16:10 filter are different shapes and are not interchangeable. Check both on your monitor’s specification, or measure the visible panel diagonally corner to corner.

Attachment varies. Frameless filters use adhesive tabs or slide into slots at the sides; some use magnetic strips. Removable versions are worth it if you share the screen for presentations.

Most filters also reduce glare and cut blue light, which is a useful side effect.

One honest note: a filter slightly dims the screen and can reduce colour accuracy, so they are not ideal for design work.

The range covers Fellowes, Kensington, StarTech, Targus, Belkin and PIXL.