Hutchinson Serenity No Flat Tire Serenity is a revolutionary tire guaranteed never to go flat The Serenity insert is designed to mimick a standard tire with 70psi of air in it. It is extremely comfortable to ride and acts like a traditional pneumatic tire Serenity must be mounted on a rim with 19mm inner width and must be installed bt a professional bicycle shop. Contact your bicycle shop for comparibility. The Serenity insert was developed by Hutshinson's aerospace division Serenity is used inmany bicycle share rental programs throughot the world.