Old fashion technology; exceptional warmth and cushioning.
After we extract the very best bison down for the socks and gloves; use the second best short down for the bison felt hats and bison fiber rugs ... the leftovers ... the tough guard hair and scruffy really short down fibers are blended with some wool in a 50/50 felt ... and die cut into comfortable, cushioning warm felt insoles.
Order a bit large and trim easily with scissors. Takes up slack in shoes and boots ... and cushions while it insulates.