A pack of 10 red latex balloons.
These latex balloons are made of natural latex and are therefore totally biodegradable. 
Size of the inflated balloon: 25 cm.
 
Warning: These balloons can be inflated with helium or air. If you fill with air, they will not float! 
Please note that the life span of an inflated helium latex balloon is a few hours, so wait until the last minute to inflate them.