What it is, and why it behaves this way
PEI is a thermoplastic used where stiffness and elevated-temperature performance matter. Stiffness means resistance to bending; it does not mean that a frame is soft or impossible to break.
Weight in context
Thin sections can help reduce material use; fittings and lenses also matter.
Flexibility & adjustment
Adjustment depends on the temple and bridge design. Do not assume the whole frame can be reshaped.
What to check when trying on
Try the actual frame for stable contact and comfortable grip.
Care & limitations
Do not use boiling water. Lens coatings, paint or adhesives may be damaged before the frame resin.
Put it into practice
Example: a resin heat rating is not a cleaning-temperature limit for PEI frames fitted with coated plastic lenses.
A common assumption to check
Heat resistance is not the same as impact resistance or finished-product certification.
Sources & scope
Page updated; sources checked: