Yes, those are surge brakes. The trailer includes a master cylinder attached to the hitch coupler on the trailer, so when the truck brakes and slows it activates the trailer brakes mechanically. If properly maintained, they work fine. I throw that in only due to your rental trailer scenario.

What they don't allow is any form of weight distribution hitch, or independent control of trailer brakes. But they do handle straightforward braking.

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2007 X3 3.0si, 6 MT, Premium, White

Retired:
2008 535i, 6 MT, M Sport, Premium, Space Grey
2003 X5 3.0 Steptronic, Premium, Titanium Silver
2002 325xi 5 MT, Steel Grey
2004 Z4 3.0 Premium, Sport, SMG, Maldives Blue