Choose 16mm for 9–11mm (total) material thickness, and 18mm for 11–13mm. Always measure your case panel + extrusion together.
📌 Example: 9mm ply + 3mm extrusion = 12mm total grip range
In this case, you’ll want to use an 18mm rivet, which is designed to grip materials between 11–13mm. If your total thickness is only 10mm, go for the 16mm rivet instead.