Built around the frame
An eyewear sleeve is specified from the frame rather than from a standard size — frame width, height and folded temple thickness all vary more between models than buyers expect. The inner face matters as much as the dimensions, because it is in constant contact with the lens. Where one pouch has to cover several frames, send the largest and smallest so the internal size is set against both rather than against an average.
How the envelope flap behaves
A flap gives a flat profile and a defined opening moment, which is why it is common in jewelry and accessory packaging. The detail that decides whether the sample is accepted is flap depth: the flap has to lie flat when the pouch is full, not only when it is empty. That depth is specified from packed thickness, and getting it wrong is the single most common reason an envelope-style sample is remade.
Approve it packed. An empty flap pouch tells you nothing about how the flap sits in use.
