LOONBALLOON Baseball Balloons, 17 inch Baseball. Quantity: 1 Accent your sports themed party with this 17in. round Baseball foil mylar balloon. The perfect balloon for your sports party, this 17in. 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. 17in. Baseball Foil Mylar Balloon