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.
One is on a pencil!
hisucolemin
Target
pencil erasers sometimes work
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.
Some are made out of animal fat and what ever rubber is made out of
Wood, the mineral graphite, and whatever erasers are made of.