they reach the same thickness of a CD) and not bonded all the way to the center. As a result, a DVD hub is weaker than a CD's, and may be damaged if stored in a case which is designed for CDs only. In addition to "pluck hubs" (which are often a simple evolution over the classical "crown of teeth"), "push-to-release" hubs are very common: in this case the hub is made in such a way that simply pushing on it with a finger compresses its component parts, thus shrinking the space it occupies and releasing the disc center; under normal situations the release cannot occur accidentally and requires someone to push on the hub (this is obviously more difficult to obtain in slim and ultra-slim cases, where in fact pluck hubs may be preferred to push-type ones). Damage risk The larger size of the keep case compared to the CD jewel box means that if the disc becomes detached from the center hub, it can move around inside the box, and the playable surface can be scratched by the hub. This can be a problem during shipping. The center "Pluck-Hubs" are designed to keep a disc in place while shipping, but can be too tight for normal home use. Because of this, the disc can be damaged upon removal due to excess warping. However, the edges of the center hub can be permanently bent in slightly to allow for a looser fit. Discs are then able to slip out easily, ideal for the home shelf. Physical dimensions Case The height and width of a (closed) keep case are fixed at 190mm (7.48 inches) and 135mm (5.315 inches), respectively. The thickness may vary to accommodate more discs ("multi" case) or to require less shelf space ("slim" or "thin" case). For a typical single-disc case it is 15mm. A keep case, thus, approximates the Video Software Dealers Association recommendation that a single-disc DVD-Video package have the same height as a VHS tape (187 mm) and the same width as a CD jewel case (142 mm). These dimensions are similar to digest size magazines. Paper sleeve The printed paper sleeve for a standard DVD case can be printed on a standard A4 sheet of paper which, after cropping, can be slipped into the outer jacket. The paper room on the front and back panels of the case is 129.5mm × 183mm and