Pad Set for USPS 11x8.5x5.5 Flat Rate Box Insulated pad set made to fit the medium 11"X8.5"X5.5" USPS Flat Rate box! Includes two 12-ounce Gel Paks! Includes packing tips to make sure your shipment is a success! The box is NOT included in the kit. The box must be acquired from the United States Postal Service. R.N.C. Industries is in no way affiliated with the United States Postal Service.