Pencil top erasers.
eraser definition by Webster's New World
Webster's New World College Dictionary Copyright © 2010 by Wiley Publishing, Inc., Cleveland, Ohio. Used by arrangement with John Wiley & Sons, Inc.
a thing that erases; specif., a device made of rubber for erasing ink or pencil marks, or a pad of felt or cloth for removing chalk marks from a blackboard
eraser definition by American Heritage Dictionary
One that erases, especially an implement, such as a piece of rubber or a pad of felt, used for erasing marks made by pencil or chalk.