The material of the digital number balloon is foil, color uniform, beautiful mirror surface shape, safe and non-toxic. Inflated: Air inflate. Self-sealing: Just put the straw in the hole and inflate it, when inflation is done just take out the straw and pinch the inflatable mouth it will be fine. Supports fluff many times to stay longer. Usage Method: Balloons have holes in the bottom and top for easy hanging with twine, string or fishing line, easily hang on strings from ceiling or attached to wall with glue point.