Nouns ending in -ette are usually feminine.
The suffix often forms a diminutive.
Is lunette masculine or feminine?
lalunette
The rule behind it
99.3% of -ette nouns are feminine
In context
Sans ses lunettes il est comme une taupe.
Without his glasses, he is as blind as a bat.
Je dois acheter de nouvelles montures de lunettes.
I need to buy new spectacle frames.
Julien a des lunettes rondes, comme John Lennon.
Julien wears round glasses, like John Lennon.