Pouch thickness is measured in microns and it decides how the finished item behaves rather than how it looks. Eighty micron stays flexible and suits everyday internal documents that get filed, pinned or passed around. One hundred adds stiffness for menus, price lists and anything handled repeatedly. From 125 upward you get rigidity for signage and long-life display. Settle the micron first, then the size — see A4 for the common one — and check it against your laminator maximum.