There are a lot of opinions on this one. I personally like flex-a-lite products. On my 06FX4 I have the "S blade" and VSC controller. The controller is very nice. It lets you control the fan in any way you want. It also ramps up the fan speed based on cooling needs. Ramping up also is easier on the charging system. on, off, auto, AC interface, adjustible turn on temp, temp probe, fuse, ect..