A feature etched in a DVD glass master which has a length of 3 to 14 timing pulses.  Information on pre-recorded DVDs is encoded into a spiral track, made up of pits.  Recordable DVDs do not have pits.  Instead, marks are created in a dye layer, or on a phase-change recording layer.  The background of this web page is made from an Atomic Force Microscope image of DVD pits.