An air-free bag
What do you think will happen if you will have a bag which can be shrinked down to the size just enough for your things so that you don't need to bring those baggy bags to school. A very small space needed for your bag and a larger space to move on.
a great relief for me!!!!
(I wish that it will be made by NIKE or ADIDAS)
Reward: at least 3 shrink bags. 1 for me and 1 for each of my 2 friends