The Disk Drive Bays
The Antec One has three external 5.25” bays, five internal 3.5” bays and two internal 2.5” bays. The 5.25” bays and the internal 3.5” bays use tool-less installation mechanisms.
Different from other cases, internal 3.5” and 2.5” units must be installed from the right panel instead of from the left panel.
Installation of 3.5” devices is made by installing a ruler to each side of the drive and sliding it into the bay you want to use.
One of the 2.5” bays is located on the bottom panel, while the other one is located on the top part of the main hard drive cage.