Gelid Solutions Silent 4 Silent 40X40X10Mm, 4200Rpm, 18.9Dba, 4.5Cfm, Rohs, 3 Year Warranty. Experience increased cooling with GELID FN-SX04-42 Slient 4 40mm Case Fan. This fan offers great performance at an affordable price in such a small package. This silent PC enthusiast dream provides additional airflow without increasing noise levels.