Dell Precision 7920 Tower Owner's Manual page 11

1. Flex 2 (default is 5.25" and Slim ODD Bay)
3. HDD fan bracket 1
5. Power distribution and fan control board
7. Flex 3 (optional)
9. HDD fan bracket 0
11. Flex 0 enclosure
2. Data cable and power cable for the Slim ODD
4. Intrusion switch
6. PSU
8. Flex 4 (optional)
10. Flex 1 enclosure
Chassis 11