It's the usual mixture of a waxy substance, a rust inhibitor and a solvent. It's sprayed on and leaves a thin, waxy residue. I have a couple patches of bare metal on the BJ8's chassis that I spray with it when I have it up on jackstands once a year or so, and the patches are shiny metal after 15 years (note I live in California, so it's easy duty).
Found this on Amazon (couldn't have said it better meself):
"This is a superlative rust inhibitor. It dries to a semi-thin soft petroleum based waxy film that completely denies gasses access to the surface it is applied to, thus it prevents rust as long as it is one the surface. Like all petroleum waxes it does evaporate very slowly, so for long-term storage cosmoline-like corrosion inhibitors may be better. This is very weather resistant, too. It beads water and is relatively abrasion resistant, though Boeshield T-9, a similar product with superior lubricity is more tenacious and water resistant. It has very poor lubricity despite it's claim as a "lubricant." In certain applications it is truly excellent: preventing freshly machined "white" steel from rusting before finishing, as a gun barrel rust preventative, on farm implements, hinges, etc. It is particularly suited to application in muzzleloading rifle barrels since it does not seem to react with Black Powder Fouling. Easy spray application gives it an advantage over "cosmoline," but it does come in more economical gallon jugs which also avoids the hazmat rip-off fee."