PERFECT SUITABLE FOR: Black number 18 foil Mylar balloons are the best choice for: 18th birthday party,18th wedding anniversary celebration,company 18th anniversary party or 81st birthday wedding anniversary party decoration.You can stick the black 18 number balloons on the wall,window or door,you can inflate with both helium or air,you can even place them on the bed, floor or table,provide your party or home a good display. PACKAGE CONTENTS: 2 Pieces 40 Inch black number Balloons:No.1 black number Balloon + No.8 black number Balloon + 1 straw. CHOOSE THEM:The black number balloon is made of high-quality aluminum film that empty balloon is 42 inch,after filled with helium or air,it's 40 inch.Please use the straw in the balloon set to inflate it slowly. TIPS FOR NUMBER BALLOONS: Due to the thermal expansion and contraction characteristics of aluminum foil,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.Please avoid leaving the balloons in an outdoor high temperature environment for a long time.If the ambient temperature is too low,it will also cause the balloon to deflate.At this point,you can use the straw to inflate again. SERVICE:We do our best to provide customers with better products. If you have any questions, we promise to give you a satisfactory answer without any delay.