Blu-ray or Blu-ray Disc (BD) is a digital data storage format for optical discs. It was designed to supersede the DVD format, in that it is capable of storing high-definition and ultra high-definition video resolution (2160p). The plastic disc is 120 mm in diameter and 1.2 mm thick, the same size as DVDs and CDs. Conventional (pre-BD-XL) Blu-ray Disc discs contain 25 GB per layer, with dual layer discs (50 GB) being the industry standard for feature-length video discs. Triple-layer discs (100 GB) and quadruple-layers (128 GB) are available for BD-XL re-writer drives. The name "Blu-ray" refers to the blue laser (specifically, a violet laser) used to read the disc, which allows information to be stored at a greater density than is possible with the longer-wavelength red laser used for DVDs. The main application of Blu-ray is as a medium for video material such as feature films and physical distribution of video games for the PlayStation 3, PlayStation 4, and Xbox One.