two pairs of glasses" or "two pairs of glass

[trueheart_205]

Is it correct if I say "two pairs of glasses" or "two pairs of glass"?
After the words of quantity "pairs/bunches/pieces" and words like that we may not add "s/es" for the nuons?
Thanks!

[SoothingDave]

If you are talking about the things you wear on your face to improve your eyesight, then they are "a pair of glasses," cause you have one lens for each eye. So if you have two such devices, then you have two pairs of glasses. For example, I have one regular pair and one tinted for driving when it's sunny.