Typically used in conjunction with a radiator but for me I wanted the noise gone concerning my bottom intake fan. How did I know a shroud would work? Because if I held the fan in my hand and moved it around the bottom intake the noise would occur once getting 15-20mm from the bottom of the case. Anymore than 15-20mm and no noise. Since a fan is 25mm thick it would space the Cougar fan 25mm from the bottom of the case thus eliminating the noise. Worked perfectly for me.