Foil balloon (also called mylars) are self sealing balloons. They are great for balloon bouquets and decorating. These are two sided with a coordinating or identical design on back. Foil balloons stay inflated for days and weeks. Use a foil tip inflator for best results. Filling these balloons with the incorrect tip (like the black rubber tip) uses more force and can cause the balloon to pop or create a leak in the seam.