The footbed is the part of a boot that wears out first and the part almost nobody replaces. A flattened insole inside a good boot feels exactly like a worn-out boot, and swapping it costs a fraction of what a resole does.
Replace like for like where the boot came with a proper footbed. Meindl's AirActive is a structured, shaped footbed rather than a flat pad, and a generic insole dropped into a Meindl will change how the boot holds the heel. The same goes for Härkila's own footbed.
Lambswool insoles add real warmth for standing still in cold weather and will compress within a season — treat them as a consumable. Leather insoles handle sweat better than foam over a long day. Latex and gel pads are cushioning for hard ground, not support.
Two practical points: take the old insole out before fitting the new one, or the boot will be half a size too tight; and dry insoles separately from the boot, which is half the reason boots never dry properly overnight.
Related: socks, laces, boot dryers, boot care, footwear.
