Carried on the hand
A wristlet is a pouch plus a carrying strap, and the strap is the part that fails first. Drop length decides whether it sits comfortably on the wrist or catches, and the attachment point takes repeated load. Both are worth confirming on a physically loaded sample rather than from a drawing.
How the zip performs in use
A zip contains contents properly and adds structure, which is why it is the closure specified wherever small items would otherwise escape. It is also the component most exposed to wear: the tape, the slider and the pull are three separate quality decisions, and a cheap zip undermines an otherwise good pouch faster than any other single part.
Run the zip repeatedly on a packed sample. Smoothness under load, and whether the slider wanders off the tape at the ends, are not visible in a photograph.
