The company recommends to use a fan grill for safety and watch out with fan controllers because this 120mm fan draws a whopping 24W. You can buy it at Koolance's webshop for only $11.99.
Specifications:
Dimensions: 120x120x38mm Type: Dual Ball-Bearing Connector: 3-pin (3-wire with tachometer) Rated Voltage: 12VDC Current: 2.0A Speed: 4000RPM (max) Static Pressure: 20.4mm-H2O Airflow: 183.5CFM (max) Noise: 59.00dBA (max)