Customized version of http://www.thingiverse.com/thing:128718

Created with Customizer! http://www.thingiverse.com/apps/customizer/run?thing_id=128718

Using the following options:

mesh_density_ratio = 98
mesh_kind = radial_circles
mount_hole_width = 32
outer_roundness = 50
mesh_clearance = 1
mesh_thickness = 1
fan_side_length = 40
solid_outer_border = 1
mesh_offset = 68
mesh_holes_d = 3
mount_hole_d = 4.1