"these beautiful slate blue balloons are truly one of a kind! Pairs beautifully with many different colors or are simply stunning by themselves! They are the perfect way to make a pop at your next event! This listing is for one slate blue balloon only. These are double layered latex 16"" balloons-this look is achieved by ""layering"" two balloons, one inside the other, to create this special shade of blue **(see below for special instructions) **if using helium, inflate day of event for best results (will not last overnight). If inflating with air, a manual (not electric) hand pump works best! String not included. Balloons will already come layered, to use just inflate as normal and tie off ends. Only the inside balloon tail needs to be tied, secure string around both and balloons are ready to go!** Balloons will ship flat and can be inflated with air or helium (can take to local party store or supermarket for a fee). Professional grade helium works best. Layered balloons.