Double layer DVD recordable disc, the wavelength of the red laser is 650nm. The capacity is 9.4GB, the once written DVD disc, both of sides can be recorded, 1X velocity is 3.49 m/s. Depending on the burning speed it can be classified to 4X, 8X and 16X disc. Burning principle is the same as the DVD+/-R. Its manufacturing technology: two pieces of the substrate with the groove is bonded together, before bonding, the groove of each substrate need to coat dyes and sputter reflective lay