I plan to ship this item in an envelope without any waterproof packaging. The shoulder straps are adjustable with elastic, so it can be used by children (toddlers) to adults. Features: * Effectively cools the body from the back. * Backpack type, so you can use both hands! * Long-lasting cooling with ice gel packs! * Includes an insulating aluminum sheet to prevent cold air from escaping! * Elastic straps are adjustable in size. Moderate thickness for a comfortable fit! * Can also be used with work clothes with fans! My Ice Back Cooler Ivory Size: W160 x H230 x D30 Set Contents: Cover 1, Gel Pack 1, Insulating Aluminum Sheet 1 Free Size Heatstroke Prevention Cooling Pack Moisturizing Gel School Backpack Rucksack Heat対策 (Heat Countermeasures)