We have the Fan/Mate 850 on our fans. Two of them, anyway. Should be the same fans, since they're both '08 models. The fan doesn't quite open all the way, but close enough to work well.
2008 King Aire 4562, Spartan K3(GT) w/ Cummins ISX 600
2014 Jeep Grand Cherokee Overland 5.7L V8 Hemi w/ Blue Ox Aventa LX Tow Bar and baseplate, SMI Air Force One brake