Start with the principle
A material label describes what a part is made from, not how its bridge meets your nose or how the temples grip. Begin with a stable fit and then compare materials in frames of suitable size.
Separate density from finished weight
Mass depends on both density and the amount of material. Lenses and fittings add to it. A thin frame and a bulky one cannot be ranked by their material names alone; ask about the complete pair you will actually wear.
Check the fit before measuring
Check bridge contact, width, temple length and clearance from your cheeks. Where a lens design needs frame-specific fitting measurements, have the chosen frame adjusted into its wearing position first. Printed frame dimensions are not a full fit assessment.
A worked example
Teaching example: a very light frame slips because its bridge does not fit, while a slightly heavier one sits steadily. The useful next step is a fit review, not a search for an even lower-density material. No particular bridge shape suits everyone.
CHECK YOUR UNDERSTANDINGDoes the lightest empty frame guarantee the most comfortable glasses?
No. Lens weight, contact area and fit still matter.
Sources & verification
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