Some manufacturers have a zero-tolerance policy with regard to LCD screens, rejecting all units found to have any number of (sub-)pixel defects. Displays meeting this standard are deemed Class I. Other manufacturers reject displays according to the number of total defects, the number of defects in a given group (e.g. 1 dead pixel or 3 stuck sub-pixels in a 5x5 pixel area), or other criteria.
In some cases, the manufacturer sends all screens to sale, and then replaces the screen if the customer reports the unit as faulty and the defective pixels meet their minimum requirements for return.[5] Some screens come with a leaflet stating how many dead pixels they are allowed to have before you can send them back to the manufacturer. Dead pixels may tend to occur in clusters; in most cases displays with such a problem can be sent back to the manufacturer.
