The HEC 66RC 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 and Micro-ATX. The dimensions of the case itself (LxWxH) are 457mm x 190mm x 410mm.

The HEC 66RC 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 nine 5.25" drive bays, which is more than enough to house various drives, particularly optical drives. With four 3.5" drive bays there is also plenty of extra HDD space as well. Installing a solid-state drive on this case would require a 3.5" adapter. Installation of hard drives into these drive bays is made all the more easier by screwless rails that allow tool-less mounting.

Made primarily of Steel, the HEC 66RC 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.