Laminating pouches come in a number of different thicknesses which are measured in Microns. Most laminating pouches will range from 150 microns to 350 microns, with those at the higher end of the scale providing a more rigid laminated document.
All pouch thickness quoted on this website are the final laminated thickness. A 150 micron for example, will be a pouch where each leaf of the laminate has a thickness of 75 micron. It’s worth checking your laminators’ user manual as not all machines are designed to handle the thicker grades of pouch.