Hasn't anyone used or seen these before? Commonly used in the recovery (tow truck) field, often for off-road recovery. Fire and rescue departments use them for rescue, heavy equipment companies use them for assembly of equipment disassembled for road transport, marine salvage companies use them to right vessels stranded on the rocks by a falling tide. OK, so the K-mart models may be iffy, but a search on Google for Inflatable Air Bag Jack gave over 82,000 hits. Even Amazon sells them.

No, you shouldn't crawl underneath it, but that is true of any jack. And, the benefit of this style of jack is that on a soft surface it is stable, unlike just about any mechanical jack.

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2008 535, 6 MT, M Sport, Premium, Space Grey
2007 X3 3.0si, 6 MT, Premium, White

Retired:
2003 X5 3.0 Steptronic, Premium, Titanium Silver
2002 325xi 5 MT, Steel Grey
2004 Z4 3.0 Premium, Sport, SMG, Maldives Blue