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Gelid Solutions Silent 4 Case Fan 4cm 40mm 4200RPM Quiet 18.9dBA 4.5CFM 24Hr Del 4897025780705 | eBay
DC 4010 5V 12V 24V DC Fan with Oil Brushless 40mm Cooling Silent fan for Laptop | eBay
Fractal Design Silent Series R3 40mm Case Fan FD-FAN-SSR3-40WT