Orders with quantities of 499 or under units are duplicated using CD-Rs. Quantities 500 or more are replicated using CDs.
The online quoter will change the type of manufacturing based upon the quantity that you enter.
The same applies to DVD-Rs and DVDs. 500 and up will be replicated DVDs and 499 and less will be on DVD-Rs.
Be sure to check out this artcle that speaks to the difference in manufacuring processes.