American Megatrends Pegasus User Manual page 6

Pegasus PCI Dimensions
The motherboard is approximately 8.55" by 13" (baby AT size). The
motherboard height restrictions are shown below:
This motherboard contains sensitive electronic components
that can be easily damaged by static electricity. Follow the
antistatic instructions carefully to ensure correct installation
2 Pegasus PCI Motherboard User's Guide
Warning
and to avoid damage.