Minimum collapsed height. The flattened body, side or remote pump and shallow saddle all exist to reduce overall height when retracted, so the jack enters a space a conventional bottle or trolley jack cannot. Every other property is subordinated to that one.

Stroke. A short collapsed height leaves less room for ram travel, so lift is limited compared with a bottle jack of the same capacity. Two-stage rams and screw extensions recover some of it, which is why extended-reach low-profile jacks exist as a distinct product.

Because ground clearance and sill profiles have reduced to the point where a standard jack will not fit beneath. A low-profile jack is often the only option that will go under without first driving the vehicle onto ramps, which defeats the purpose if a wheel needs removing.

Considerably, and it is easy to overlook. A jack that fits under the vehicle but leaves no room to swing the handle has solved only half the problem. Long detachable handles and remote or side-mounted pumps exist specifically to address that, and are worth checking before buying.

Not inherently, but the low saddle and short lift mean the working range is narrow, so the load should be transferred to stands promptly. As with any jack, the ground must be firm and level and the lifting point sound - the low profile changes access, not the physics.

Capacities overlap, though for a given capacity a low-profile jack is physically larger in plan because the same force has to be produced in a shorter body. The choice is driven by the clearance available rather than by capacity, which is usually the easier requirement to satisfy.

A ram with a second, smaller-diameter stage that extends after the first, giving more total lift from the same collapsed height. Force falls on the second stage because the effective area is smaller, so the rated capacity typically applies to the first stage rather than throughout the stroke.