Bumper

Rubber is a soft, bouncy material used by the Pigs in Angry Birds. It first appears in Danger Above, and is represented as purple ovals connected to each other.

Rubber, was made to repel the Birds and essentialy, cannot be destroyed. Whenever a bird hits rubber, it will bounce back and make a "sproing" noise. Rubber functions similarly to Floaties and umbrellas in Angry Birds Rio.

Objects can also be bounced around with rubber, such as Stone balls or Wood planks, but are damaged each time they hit the rubber.

In some cases, rubber can be quite a nuisance to the player, for example, the player tries to aim a bird at the pigs, and accidentaly hit the rubber, therefore, wasting a bird, and having to retry the level.

Trivia
Rubber, along with Eggs and Ground are the only indestructable objects in the game.