A fan is provided herein, including a housing, a hub, and a plurality of blades. The housing includes a top case and a bottom case. The hub is rotatably disposed between the top case and the bottom case in an axial direction. The blades extend from the hub in a radial direction, located between the top case and the bottom case. Each of the blades has a proximal end and a distal end. The proximal end is connected to the hub. The distal end is opposite from the proximal end, located at the other side of the blade, having at least one recessed portion. Each of the recessed portions form a passage for air.