there are 2 different manufactures of these. i have been using them since 1997 . there is a 5 lb cylinder of drying asgent that is renewed by baking in an oven.
i have a really bad back that makes wallkimg the swap meet impossible. therefore i usually only do 1/2 day on friday and then show on saturday. combine that with a 350 mile drive and then parking my car in a hay field on friday it made me decide the last 2 years to stay home. i greatly doubt i will ever be there again.
unfornately my wife is disabled and cant walk the swap meet. i have chronic knee and back problems. so for us t had become a 6 hour drive to sit behind our car on saturday. the last 2 years we have decided its too far for that.