Buy a Protective cap – leave the filter on, pack safely
Once a filter is mounted you don’t want to unscrew it every time you pack up – but the original lens cap no longer fits over it. That is exactly what a Protective cap is for. It closes flush over the mounted filter and shields the glass and its coating from everything else in your backpack. NiSi has caps for the common filter diameters and systems, magnetic or clamping, so they stay put on a hike and come off in one move. Your setup stays complete and protected at the same time. Buy your Protective cap now.