EDIT: The air flow guide was about 1mm too tall which caused a slight bowing on the top grid. I modified the STL so it is all good now.
The Thermaltake Tower 100 is a great case, but hot air tends to accumulate in the top part of the case. Moving the fan “outside” the case into this top chamber does help, but air still tends to circulate in this top part.
This exhaust helps guide the air out of the case, preventing the accumulation of hot air.
The author marked this model as their own original creation.