3M Privacy Filters keep confidential information private. Only persons directly in front of the monitor can see the image on screen; others on either side of them see a darkened screen. Custom fit to your Apple iMac 21.5-inch. The filter application system features an optically clear adhesive designed specifically for display screens. Testing proves that, when kept clean, the filter can be repositioned hundreds of times. Reversible, matte side reduces glare and reflections. Lightweight, thin, frameless design. Protects display from dirt, debris and scratches. Cleans easily with a soft cloth and water. Great for high traffic areas such as airports, airplanes, commuter trains, coffee shops and other public places.