The Power Macintosh computers, such as the 7200, 7300, 7500, 7600, 8500, 8600, 9500 and 9600 support two different sizes of PCI cards in any of the PCI slots: 7-inch x 4-inch, and 12-inch x 4-inch.
The Power Macintosh 4400 has two PCI expansion slots, and one slot accepts only 7-inch PCI cards, but the other slot accepts either 7- or 12-inch cards.
Finally, the Power Macintosh 5400, 5500, 6400, 6500 and Macintosh Performa 6400 series, and Macintosh Performa 6360/160 computers support only 7-inch PCI cards.
The PCI local bus Specification 2.0 list the exact dimensions as:
In Inches 6.875 x 4.2 and 12.283 x 4.2
In Millimeters 174.630 x 106.68 and 312 x 106.68