MASSCOOL Hard Disk Cooler FHD-4B02S4 MASSCOOL 4B02S4 Hard Disk Cooler 4B02S4 Hard Disk Cooler, Fan size: 2 x 50mm. Fan size: 50mm, Bearing Type: Sleeve, RPM:4800RPM, Air Flow: 2 x 9.43CFM at 4800RPM, Noise Level:27.7dBA.