LoonBalloon TENNIS Yellow Ball Sports Birthday Party 2 18in. Mylar Balloons, Accent your tennis themed party with this 18in. round Tennis Ball foil mylar balloon. The perfect balloon for your tennis party, this 18in. party balloon is great for setting the scene! This balloon includes a self-sealing valve, preventing the gas from escaping after it’s inflated. The balloon can be inflated with helium to float or with a balloon air inflator. Balloon arrives uninflated. 18in. Tennis Ball Foil Mylar Balloon, Accent your tennis themed party with this 18in. round Tennis Ball foil mylar balloon. The perfect balloon for your tennis party, this 18in. party balloon is great for setting the scene! This balloon includes a self-sealing valve, preventing the gas from escaping after it’s inflated. The balloon can be inflated with helium to float or with a balloon air inflator. Balloon arrives uninflated. 18in. Tennis Ball Foil Mylar Balloon