PWM Small package sizes that perform and only have the current consumption of a typically standard size fan .
Many other brands Pwm are very expensive double the cost , double the size
12 inch fan with 2100cfm ,,no pressure drop or at approx 1/2inch pressure drop around 1800cfm [pressure drop is what the resistance of the rad core does to airflow ]
All this for under 15amps current draw
Short size fan shroud as well
can be run 2 ways , with /with out PWm controller
fans are about 1.5x ---2 x the cost of a normal setup

By comparo a 350mm /14 inch medium level fan at 1/2 inch pressure drop flows 850cfm ---1100cfm draws 14---20 amps

DeltaPAG_Cataloge.pdf (shopify.com)