The utilitarian steel gray enclosure measures 175mm L, 85mm W, and 70mm H (6.9" x 3.3" x 2.8").  The rear panel features a standard AC power cord receptacle and vent holes to let the exhaust air out.

The SS-300TFX uses a single 80mm Adda fan, which blows air into the PSU (#AD0812HB-C70) for cooling.   

Here are a few more pictures showing the layout and components inside the Seasonic SS-300TFX power supply.  The overall layout, build quality and component selection appears to be very good as we have come to expect from Seasonic.