Summary

I made this air grill to ensure high airflow for a 100mm hole (pipe).
The principle behind this air grid is to get the maximum possible flux, without throttling it.
Many of the grids avalable on the market fit into pipe slowing down the air, in this case I chosed to keep an increased diameter to get in fresh air, still filtering insects. A back connector with 97mm is available if you don' t want to fix the grid with wall plugs.