Silver number 21 foil Mylar balloons are suitable for girl's 21th birthday party, sister's 21th birthday party,wedding anniversary celebration and many other party decoration.2 Pieces 40 Inch silver number balloons:No.2 silver number balloon + No.1 silver number balloon + 1 straw.The silver number balloon is made of high-quality aluminum film.Please use the straw in the balloon set to inflate it slowly.Please avoid filling more than 90% of air or helium.If it is over-inflated,it can easily cause the balloon to explode at high temperatures.You can reused the foil Mylar balloons.If you are not satisfied with the balloon,just contact us get a full refund or free replacement.