Generally speaking, it refers to the album released by the record company after the singer or group retires or disbands. Unlike the featured album, this album will completely include all the albums/singles during the artist's debut. It usually comes with an album, a DVD of MV/LIVE, an employee pass, a copy of past concerts or an autograph. Collections are usually made into luxurious big boxes, so they are called superior boxes. Generally speaking, this kind of box needs to be produced by appointment, which is generally impossible to start in ordinary CD shops. The price should be around tens of thousands of yen. But the styles are generally luxurious, and the premium box is very collectible.