What is the purpose of a fan shroud?
Fan shrouds can increase the efficiency of the cooling system by allowing the fan to draw air more evenly across the core of your radiator.
How? Instead of a fan just pulling air across its diameter, a shroud enables the fan to pull air from the entire area of the core and out through the back of the fan.
3 Series fan shrouds are available right here:
https://mp-uk.com/