AC Infinity AI-MPF140A MULTIFAN S4 140mm Quiet USB Cooling Fan can be positioned to stand upright or laid flat to cool various electronics and ventilate DIY projects. Features a multi-speed controller with power switch. Includes anti-vibration rubber feet and a 6-foot power cord. The low power-consumption fan be be powered by USB ports found behind popular electronics and on portable power banks. Each unit contains an additional USB port, up to four fans can be daisy chained together to share the same power source. This fan system is CE and RoHS certified and contains premium dual-ball bearings, allowing it to be mounted horizontally or vertically.
 
Features:

• Compact and energy-efficient USB fan designed various DIY cooling and ventilation projects.
• Features a multi-speed controller to set the fan's speed to optimal noise and airflow levels.
• Dual-ball bearings have a lifespan of 67,000 hours and allows the fans to be laid flat or stand upright.
• USB plug can power the fan through USB ports found behind electronics and on portable power banks.
• Dimensions: 1.6 x 1.6 x 0.8 in. | Airflow: 12 CFM | Noise: 18 dBA | Bearings: Dual Ball

 
For electronics and components that requires more airflow; each fan unit can daisy chain additional MULTIFAN S series fans. Up to four fans can share the same USB power source; and up to six fans can share the same thermal controller (sold separately). MULTIFAN S1, S2, S3 and S4 contains one fan, and MULTIFAN S5 and S7 contains two fans.