High-quality yet cheap synthetic "felt" insoles from the German army. Unissued military surplus. These things are made for marching but hiking they’ll also do without needing some drill sergeant yelling next to you.
Made of soft-ish synthetic felt material that forms to your feet. It's just thick and spongy enough to talk about a nominal shock absorption feature. What makes these really nice is the breathable construction without PVC or rubber layers anywhere. Just make sure the insole fits tight in the boot.
The sizes are in Mondopoint, which is the length of the foot in millimeters. The insole is a few mm longer than the given measurement. We have added the corresponding EU/US sizes in brackets.
The insoles can be freely tailored to fit with just a pair of scissors. Alternatively you can purchase a pair of too large insoles and cut them to shape.
Unused Bundeswehr, a.k.a German military surplus. Nobody has stomped or sweated on these. So, a very nice deal indeed.