Newegg offers the Cooler Master SickleFlow 120mm LED silent fan for just $5 shipped, which is a solid 50% off the typical retail price and a little less than 50% off the current Amazon Prime shipped price. These are a solid and popular option for mining rig cooling thanks to their reliability and low price. This low price is even lower than usual, and ships free with Super Eggsaver.
R4 series fans offer a unity of maximum rotational speed and optimum airflow. Using a unique long-life sleeve bearing fan, the R4 series offers long life rating of 50,000 hours. R4 series fans perform at a maximum of 69CFM at 2000RPM. They also feature light-brown transparent fan blades for better LED effect.