How many external and internal drive bays does the Athena Power RM-3U300P608 feature?

The Athena Power RM-3U300P608 features three external 5.25" drive bays and two internal 3.5" drive bays or three 2.5" hidden bays.

What is the maximum motherboard size that can fit in the Athena Power RM-3U300P608 rackmount server case?

The Athena Power RM-3U300P608 rackmount server case is compatible with MicroATX (9.6x9.6), ATX (12x10), and Mini-ITX (6.7x6.7) motherboards.

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Athena Power RM-3U300P608 Black Aluminum / Steel 3U Rackmount Server Case 600W 80 PLUS Bronze 3 External 5.25" Drive Bays - OEM