Size: extreme small size (9 x 7.4 x 3.5in ) design to fit in both Mini-ITX motherboard and Flex PSU (5.9 x 3.2 x 1.6in). Cooling system: abundant heat emission holes including front panel, are designed to solve common cooling problem of mini computer case. Extension design: a slot of PCIE, two WIFI holes, and two USB 3.0 and HD audio. CPU cooler: no taller than 75mm when install a M.2 hard disk; no taller than 60mm when install a 2.5” SSD on top; no taller than 45mm when install a 3.5” HDD on top. Portability: small volume (3.8L) allow it easy to be put in backpacks, luggage and on desktop.