The iMac has a G5-based logic board, widescreen flat-panel display, slot loading optical drive, hard disk, stereo speakers, and power supply all located inside a two-inch thin enclosure. The iMac G5 comes in two sizes, the 17" iMac and the 20" iMac. The luminous twin layer plastic enclosure hangs suspended from an anodized aluminum stand attached at its center of gravity. The foot is formed from a single sheet of anodized aluminum that rolls into the rear of the enclosure with no visible mechanism. Adjustments to the iMac's display viewing angle can be made by the touch of a finger. The iMac tilts from 25° to -5°. Three quiet blowers draw cool air into the system through the speaker grills. Thermal software spins them as fast or slow as needed for a quiet operation. A slit in the back of the case allows heat to rise out the top. By unfastening three screws along the bottom edge, the rear cover can be removed exposing the whole system for upgrades and service.