Airless Foam Tire Inserts - Click Here for Catalog Made from our proprietary AERO-FLEX® cellular polyurethane foam, CEW’s flat proof tire inserts duplicate the ride comfort of air-inflated tires with total freedom from flats, leaks and repairs. We at CEW carry a rich inventory of flat proof pneumatic tires with solid inserts or can provide just an airless insert only. Foam Tire Insert Products