The Mini Balloon Kit is based around the 36 inch wide mylar foil balloons found by contributor @patcoyle -- which are much cheaper (as little as $3 each!), and can stay inflated for over a week. They fit in the back seat of your car, or can be taken on the subway. Heck, unlike the big red rubber balloons, they fit through a doorway and can be stored indoors. They do lift much less than our standard rubber weather balloons, however -- see below for more!