All mainstream optical discs, from the oldest CDs to the most recent high-capacity DVDs, are based on the original CD specification. The dimensions of a standard CD or DVD are 120 mm in diameter (60 mm radius) by 1.2 mm thick, with a 15 mm diameter central hole that accommodates the rotating center spindle of the drive.
Commercial CDs and DVDs are produced by a physical stamping process, and are referred to as pressed discs or stamped discs. Commercial discs may be one-sided or two-sided, and the data side or sides are nearly always a reflective silver color. Writable discs are produced by the operation of a relatively high power laser on a layer of dye or another substance that can be altered by light, and are always one-sided. The data side of a writable disc may be nearly any color, from a metallic silver or gold to yellow-green to a dark blue. It is not possible to identify the type or quality of a writable disc by visually examining its data side.
Despite their similarity in appearance, there are many differences between discs. Discs vary in the writable standard they support, the dyes and other materials they use, compatibility with different models of writers and players, archival stability, and overall quality.
Although CD writers are obsolescent, writable CD discs continue to sell by the billions. Writable CDs are cheap—even premium brands can be bought in bulk for as little as $0.10 each when they're on sale—and are ideal for duplicating ...