Looking for maximum airflow through your hood? These Singular louvers were designed specifically for the Miata. They'll increase the airflow through your radiator as well as add front downforce - it's all good.
The louvers do require you to cut into your hood, of course. But there's a good reason for that. To make installation as easy as possible, they come with clear instructions and a stick-on vinyl template to ensure you position them at the lowest pressure areas. These locations were determined by actual testing for the best airflow, and Singular reports a 50% drop in underhood pressure. There are even integral Gurney flaps ahead of the louvers to add to the efficiency.
Installing the louvers under the skin of the hood takes a bit longer, but makes for a very clean look. The kit even includes rubber trim for the opening. You can also rivet them in from above, which is considerably quicker.
This particular set was designed specifically for the NC chassis Miata, but it can be used on almost everything. They're big for maximum flow.