They, are referred to as ‘systems», since the fexible wrap products are fire tested in conjuction with the duct to be protected. thus they are not fire rated wrap «products», rather the product and duct tested together become de fire resistence-rated duct «system». in contrast, a gypsum shaft assembly is not actually tested as four walls enclousing the duct, but rather as an individual shaftwall, which is clearly not a duct «system».