Full layer of premium lamb''s wool attached to an anti-slip perforated latex base. After normal day-to-day wearing, the friction caused by movement of your feet will produce a layer of felted wool. We understanding trimming to the correct size could be frustrated, so that is why we have trimmed them to fit into most regular shoes and boots, while not as wide as a shearling boot replacement insole. It is made of wool trimmed from the hide and attached it to a latex bottom.