Dose this need the red hardener or dose it air dry

It comes with a white tube hardener lodged inside the cap. If missing then either someone stole it or went missing during transport.

Comes with the hardner just like automotive Bondo. It's white and if you careful and read instructions the tube will treat the whole can. Mix small amounts, take your time. I mixed a little more hardner one time it set too quick and too hard. It broke apart when sanding it. It kind of works like drywall putty, if mixed right you can really smooth it in and sand lightly later

yes it has to have a harder or it will never get hard or stick

I was wondering the same thing, looking at the product photo, at the bottom. It states it contains 1 oz of hardner.