PC Case Sizes: E-ATX, ATX, mATX, and ITX Compared | GPCB
Mid Tower PC case, Includes 4 x 120mm Umbra Void fans, Up to an E-ATX motherboard, 7 + 3 expansion slots, Tempered glass side panel, Up to 380mm long GPU.
The right way to put RAM in your PC's memory sockets | PCWorld
The kind of motherboard you pick highly affects the performance of the PC since all sizes of motherboards come with different numbers of expansion slots and support different kinds of hardware.
Types of Expansion Slots in the Motherboard
Expansion slot covers are used to protect unused expansion slots on a computer case. These covers help to prevent dust and other debris from entering the system and can also help to improve airflow through the case.