ah, probably it's HD-DVD, from another source:
"此外,HD DVD碟片記錄容量雖較小,但防刮、防污能力好,不需卡匣,因此生產製程較容易且成本較低"
translation:
"in addition, although HD-DVD disk has a slightly smaller capacity, it is more scratch-resistant and dirt-resistant, doesn't need cassettes (???), that's why the manufacturing process is easier and has a lower cost."
the Wii is an epidemic.