CD replication is the manufacturing process used to produce 500 or more copies of a CD. CD replication is used for these larger quantities because although the set-up costs of CD replication are very high, it is very cheap to produce each unit once the process is going. CD duplication set-up costs are low, as all that is required for CD duplication is a blank CD-R and a CD burner, which is why CD duplication is used for smaller quantities.