7" and 14" will not float with helium. 7" numbers and letters must be heat sealed.
Please note: Foil balloons do not expand like latex balloons and hence they burst if you overfill it. Foil balloon comes FLAT and UNINFLATED. Foil balloons must never be released outside as they do not bio-degrade and also they may conduct electricity. Do not expose foil balloons to extreme heat or they can burst.