rubber eraser vs pencil eraser

rubber eraser and pencil eraser both are nouns.

Word	Noun	Adjective	Verb	Adverb
rubber eraser	Yes	No	No	No
pencil eraser	Yes	No	No	No

As nouns, rubber eraser and pencil eraser are synonyms defined as:

rubber eraser and pencil eraser: an eraser made of rubber (or of a synthetic material with properties similar to rubber); commonly mounted at one end of a pencil

Other synonyms of rubber eraser include rubber.

rubber eraser (noun)	pencil eraser (noun)
an eraser made of rubber (or of a synthetic material with properties similar to rubber); commonly mounted at one end of a pencil	an eraser made of rubber (or of a synthetic material with properties similar to rubber); commonly mounted at one end of a pencil