Like a normal envelope with bubbles on the inside, self-seal bubble mailers are able to protect its contents from bouncing around while in transit. This is especially valuable for items such as damaged books, rare trading cards, CD’s, DVD’s, and other fragile objects. The bubbles are simply air pockets, which absorb the impact from bouncing around. Many bubble mailers require something external, such as tape, to seal them up, but self-sealing mailers do not.