You don't, Your just buying pencil top erasers.
one erases pencil marks and the other erases pen ink
it dries out
No.
Nope, erasers too.
An eraser is used to remove pencil marks or mistakes on paper by rubbing them away. It helps to correct errors and make revisions on written or drawn work. Erasers come in various forms such as pencil erasers, kneaded erasers, and electric erasers.
One is on a pencil!
hisucolemin
Target
In 1770, a vegetable gum that could take away pencil marks was dubbed "rubber" by Joseph Priestly. Edward Naire, however, was the first one to widely-market this substance as rubber erasers.
Wood, the mineral graphite, and whatever erasers are made of.
Some are made out of animal fat and what ever rubber is made out of