I have two Blue Ox immobilizers. One where the drop receiver goes into the motorhome receiver, and one where the tow bar goes into the drop receiver. They work well.
2008 King Aire 4562, Spartan K3(GT) w/ Cummins ISX, Motosat HD-SL5 w/ SWM-8, Multiswitch, HR34 Genie
2014 Jeep Grand Cherokee Overland 5.7L V8 Hemi w/ Blue Ox Aventa LX Tow Bar and baseplate, SMI Air Force One brake