This is a Fan Cool Down Shroud design to bring your motor back down to temperature after a run.  This is the Shroud only, fan is not included.  This is designed for 40mm fans.  There is a link below to the fan I purchased.  These come in a variety of colors.
 
https://a.co/d/585bmms
 
NOTE:  3D PRINTED PRODUCTS MAY NEED TO BE PRINTED AND MAY TAKE A FEW DAYS TO SHIP.