The Antec Nine Hundred has a the ATX form factor. ATX is the most ubiquitous of case standards, providing the largest array of compatible hardware on the market. Using the ATX standard, the case can house motherboards and power supplies with form factors ATX, Micro-ATX and Mini-ITX. The dimensions of the case itself (LxWxH) are 467mm x 206mm x 493mm.

The Antec Nine Hundred has seven expansion slots, so there is plenty of room for extra components, which may be a deciding factor when planning on the longevity and build type of a PC system. The case has three 5.25" drive bays, which is enough to house an optical drive and a couple of hard drives, while still having space for plenty more HDDs with the six 3.5" drive bays that are also available. There are no 2.5" drive bays, though, so any SSD or laptop-sized HDD installation would require an adapter.

Made primarily of Steel, the Antec Nine Hundred is built to be strong and well-ventilated. Steel cases are generally fairly cheap and sturdy, but also tend to be quite heavy. Whatever your case's material, it is important to keep a consistent airflow so that heat doesn't build up inside. It is therefore advised that you make use of the available built-in case fans and fan installation sections.