Micro-ATX (specifically designed for Dell chassis). Expansion: 1 x PCIe x16 (for graphics cards) 1 x PCIe x1 2. Rear I/O and Connectivity
Sources: [17†L20-L43]
4-pin connector with PWM speed control for the processor cooler. mih61r mb 10097-1 manual
Ultimate Guide to the MIH61R MB 10097-1 Motherboard: Manual, Specs, and Troubleshooting Micro-ATX (specifically designed for Dell chassis)