to prevent scratches and do not need a caddy.

Caddies may be an integral part of the medium, as in some DVD-RAM discs, or separately attached.

Examples

Caddies date at least to the Capacitance Electronic Disc, which used a caddy from 1981 to protect the grooves of the disc.

Some early CD-ROM drives used a mechanism where CDs had to be inserted into special cartridges, somewhat similar in appearance