So the first bit on the left is an adaptor so it can fit over the Nissan bottle jack, piston head, I suppose you call it. The middle bit is just an extension piece, which fits over the first bit, so the vehicle can be lifted higher that what the jack can.The third bit, on the right fits on either the left of middle bit, or both together if needed, and goes under your axle when jacking up.
Hope this makes sense.
These are handy so you can use the OEM bottle jack when you have bigger tyres.