These emergency mylar blankets are reusable, waterproof, and windproof.  The body heat is reflected back to the user. Each blanket is individually sealed and measures 4″ x 3″ folded. They unfold to 84″ x 52″. There are 50 per pack, so order 2 packs for a 100 bag event and order 10 packs for 500 bag event.