Silver Foil Bubble Mailer Envelopes 6" X 9" - 50/Case Foil Bubble Mailers by Cool Blue costs less than traditional foam and ideal for cold shipping. Foil reflects 97% of radiant heat and acts like a shield against three types of heat transfer: conduction, convection and radiant. Costs less than traditional foam insulation. Bubble laminated for durability and protective cushioning. Cool Blue bubble interior, silver foil outside. 25/Case.