I just got one of these quad fans (they also make a dual fan). I have been wanting a multiple fan for some time now, but other quad fans were $200 and I wasn't ready to spend that much for a fan. This one is only $40 and I am very happy with it so far (once I figured out how to install it in the canopy). I needed more fan power, but I didn't like all the extra plugs. This has one plug for the 4 fans, and it is pretty quiet. I also have a single fan that turns on first so this only kicks on when the temp in the tank rises more than the single fan can handle. Although it has clamps for mounting, they were too narrow for the wood frame of my canopy and or the edge of my tank. Instead I attached it to the canopy with an eye hook and some framing wire like I did my single fans.
Fluorescent Terrarium Lighting and Cage Accessories: Azoo Cooling Fans at Drs. Foster and Smith