A mini-ATX casing is a common computer case and resembles the ATX casing. This kind of computer case is also called a midi tower. You can place an ATX motherboard in this case, so you place more expansion cards than in a smaller casing. For example, you can build a complete gaming PC with an ATX casing or a computer that you place on or under a desk in an office setting. The case is also more future-proof in terms of storage.