This is a cooling fan shroud for the Anet A8 power supply. It was designed to fit the 20 Amp version, which is 110mm wide and 50mm thick. This shroud provides two air flow paths, through the case as well as over the top panel which the power supply uses as a heat sink. The fan should be oriented so it pulls air in through the power supply blows out and away from it. This shroud accomodates a 50mm box fan.
Added a second version that fits an 80mm fan. This one is untested, so please give feedback if you print it.