Fits: All E46 Non-M & M3 BMW's

Benefits:
-Relieves air pressure beneath the hood/bonnet (reduces lift)
-Pulls hot air from the engine bay in motion (improved cooling)
-Creates an opening directly above the exhaust manifold (reduced heat soak)
-Fits between the existing bonnet bracing (un-compromised structure)
Note: This vent come in a flat sheet and is bonded to the underside of the bonnet. 

Material: 
-Aluminium - Raw
-Rivets & templates included

Heat under the hood/bonnet can be significant and increases with revs & load. This energy convecting into the air and radiating off the manifold and block makes the engine bay a literal oven. This heat is absorbed by nearby components with the only means of escape being air flow down the narrow and turbulent transmission tunnel. 
Releasing this heat through the hood of a car is a great way to reduce engine bay temps, reduce front lift and promote airflow through the radiator for more efficient cooling. 

The CMP hood vents are installed from beneath with either rivets or epoxy and designed specially for the E46 chassis to maintain under bonnet airflow where it is needed then expel it directly above the exhaust manifold to promote natural convection at a stand still.
The effectiveness of these vents increase with speed as the leading gurney flap increases the pressure differential to pull the hot air out. 

Installation is as simple as lining up the vent tabs against the bonnet bracing to take the guess work out of getting the correct position and angle followed by drilling some holes and connecting the dots with a rotary tool before bending to the desired angle of attack and painting.