Material of Digital Number Balloons is foil, color uniform, Beautiful mirror surface shape, safe and non-toxic. InflatedAir inflate. Self-sealing: Just put the straw into the hole and inflate it, when done the inflation just drew the straw out and pinch the inflatable mouth then will be fine. support inflate many times for longer staying. Usage method: There are holes on the bottom and top of the balloons for easy hanging with twine, string, or fishing line, easily hang on strings from ceilings or attached to wall with glue point.