This case has nine 5 ¼” bays, coming with a removable hard disk drive cage for three hard drives that takes up three of these 5 ¼” bays (the front 120-mm fan is attached to this cage). The case also comes with one bay adaptor to convert any of the 5 ¼” bays into a 3 ½” bay for installing a hard disk drive or a floppy disk drive. The 5 ¼” bays use a screwless mechanism to hold optical drives, the HDD cage and the adaptor.
So there are several possible disk drive configurations for this case. The standard configuration will give you three internal 3 ½” bays for hard disk drives, one 3 ½” for either another hard disk drive or a floppy disk drive and five 5 ¼” bays. If you don’t use the adaptor then you have six 5 ¼” bays. If you remove the HDD cage you have all nine 5 ¼” available, but this is an unrealistic scenario, as all computers need at least one hard disk drive. If you really need a lot of 5 ¼” bays, then you can remove the HDD cage and install just one hard drive on the adaptor, allowing eight 5 ¼” to be available.
The big question is: who needs that many 5 ¼” bays? We think that M9 would be a far better product if it included a second HDD cage. This would expand the number of internal 3 ½” bays for hard disk drives to six (or seven, if you use the extra adaptor), giving you three (or two, if the adaptor is used) 5 ¼” bays, which is more than enough even for a hardcore user.
Maybe Thermaltake did this thinking of users willing to install one of their water-cooling systems that use 5 ¼” bays. In any circumstance, these users could simply remove the extra cage if they needed more 5 ¼” bays and, at the same time, provide more internal 3 ½” bays for the users that need to install more hard disk drives.

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Figure 11: Hard disk drive cage.

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Figure 12: Hard disk drive cage outside the case.

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Figure 13: Hard disk drive cage outside the case.
You can not only remove the hard disk drive cage from the case to facilitate the installation of hard disk drives, but you can also reinstall it anywhere you want. It comes installed on the lower three 5 ¼” bays, but on Figure 14 we moved it to the middle three 5 ¼” bays. Before moving it to a new location you will need to break and remove the metallic cover that exists on the other 5 ¼” bays.

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Figure 14: Hard disk drive cage on a different position.