... not wet the dest, even for long-time running USB320Mini USB Air Humidifier Professional design, no visible screw and screw hole ... Ultrasonic Technology, Micro-Holes Mist TechonogyWith switch-power adaptor, and USB connector. Applicable place: rooms(bedroom, living room, yoga room), ... hotels,hospitals, SPA circumstances. office, corridor, and etc. Applicable space: 15 square meters USB Air Humidifier