Thermaltake Mobile Fan II External USB Cooling Fan for Notebook & Desktop. Thermaltake convenient solution with extremely mobile concept inside. Perfect accessory for NB & PC. Directly plug into USB port. Unnecessary additional power supply. VR knob : Adjust fan speed manually. One-touch retractable USB power cable box. Slim USB power cable, only 0.6 mm in depth. With badge fan grille to avoid touching accidentally. -Operating Range - 3.