The interior of the Antec One case is not larger than that of a common ATX case; however, there are plenty of differences between a common essential case and the One. The entire interior of the One is black, which does not really matter though as the case does not have a windowed side panel. The motherboard tray forms a very large opening behind the CPU, allowing the installation of large CPU coolers without the need to remove the motherboard from the case. However, the width of the case allows for the installation of coolers up to 15cm tall, meaning that monstrous coolers like the Noctua NH-D14 and the Phanteks PH-TC14PE will not fit. There are openings for routing some cables as well, none of which however have rubber grommets installed.
At the rear and top panels of the case a typical black 120mm cooling fans have been installed. It is interesting that Antec is using all-black cables and connectors for the otherwise plain cooling fans.
Antec placed the 3.5" bays facing sideward, thus allowing the installation of long PCI Express cards without the worry that they might be blocked by a drive. The 3.5" drives may be installed by using the simple plastic rails provided with the Antec One by inserting them from the right side of the case. Simple plastic tool-less securement mechanisms are being used to hold 5.25" devices in place, yet screws may also be used if that is deemed necessary.
Our ICTT system fit inside the Antec One without issues. A full ATX motherboard would end right over the cable openings, leaving little room for maneuvering. Installing a very long graphic card should not be a problem; the way to the front of the case is all clear. The bottom 120mm fan slot however will become unusable if the power supply chassis is longer than what the ATX design guide dictates and, as we mentioned above, the installation of overly tall CPU coolers is not feasible. A typical home/gaming system should fit very comfortably inside the Antec One, although a large number of components and cables may easily create a chaos.