These are Made of high quality aluminum foil, about 16 inch 0 to 100 Number Digit and 16 Inch Happy Birthday Alpabets, thick and auto-sealing, no leaks, can last for days when inflated. Give Your Big Party A Personalized Presentation With Foil Balloons! This Collection Of Metallic Balloons Features Every Alphabets From A to Z and Numbers, So You Can Mix And Match To Form Any Number Or Happy Birthday Letters. Whether You'Re Celebrating A Big Birthday, These Shining Happy Birthday silver foil Balloons Are Perfect For Your Celebration. Mix And Match With Coordinating Foil And Latex Balloons accessories16" Inches Happy Birthday Balloon X 13 Alphabets16" Inches Number Balloon X 2Colour: SilverBirthday Occassions For Kids, Girls, Babies, Infants, Boys, Mom, Dad, Brother, Sister, Husband, Wife, as well as Boyfriend & Girlfriend Surprise Birthday PartyThese are self-sealing balloons. Tying with fingers is not needed. It has Self-sealing and is reusable. The foil balloons automatically seal when you stop filling them ?Tying, twisting, or Putting a knot is not necessary.?hoto friendly. Numbers and Letter balloons simply can be used as props or to decorate your wall with them.