8 Black Number Shape Mylar Foil Balloons 26 Number Eight 1 Mylar Balloons. Self-sealing, with Hang Tabs. Designed for Helium Fill to Float. Or can Air Fill to Hang. This Medium Size Black Number balloon is 26 Inches an are great for bouquets, photo backdrops, on the top of balloon columns, incorporated into a balloon arches and more. These balloons use a lot less Helium than a standard 34? number.