The rear of the Zalman HD135 Aluminum HTPC Case has been sanctioned off into three sections with the PSU mount on the very left. The middle portion of the case features optional dual 60mm fan mounts which act as exhaust blowholes. Below the fan mounts is the ATX I/O back plate for a mATX or standard size motherboard. To the right of the case are seven slots to install any combination of PCI/PCI-E and AGP expansion cards. One point to note about the PSU mount is that Zalman has lowered the position of this area in order to allow consumers to install a full sized PSU as well as keep the HD135 design low profile.