Abstract: Presented is a support structure for annular magnetic recording disks of the "hard" type used in computers. These types of disks are not usually manufactured by the same manufacturer that manufactures the disk drive mechanism. In many instances the disk drive manufacturer is far removed from the disk manufacturer and as a consequence the disks must be shipped to the disk manufacturer for installation in the disk drives prior to incorporation in the completed computer. The disks are highly susceptible to contamination from a variety of sources, and must therefore be handled with extreme care to avoid such contamination. The support structure of this invention constitutes an expandible and contractible mandrel designed specifically to interact with the inner periphery of the annular magnetic disks in such a manner as to support a multiplicity of the disks in spaced parallel relation.