Minimax Compact Discs are generally CD singles which consist of a 3-inch playing area (equivalent to the mini CD single) surrounded by an area of translucent plastic (either clear or coloured) to make them full-size Compact Discs. The playable part of the disc conforms to Red Book standards.
On a normal Compact Disc, the reflective layer would continue to the edge of the disc, even if there was not enough music to fill it.
Because of the small playing area, minimax CDs can only hold a limited playing time (about 24 minutes maximum) and so have only been used for music singles or EPs.
They are very uncommon, presumably because of the extra expense in manufacturing them over a standard 5-inch CD single, but have been used for special edition singles, in much the same way as coloured vinyl records. It could be argued that the holographic CD is a form of minimax CD, as it is also formed of a mini CD single inside a larger area of plastic containing the holographic design.