This light weight liner offers 100% waterproofness, keeping your feet dry in all conditions. The shaft height supports the shell and provides additional stability. Ideal warmth to weight ration. The liner fits perfectly with our expedition boot Polar A/P/S. If you want a tight fit, choose your regular boot size for the liner. If you prefer more room in the liner, choose one size up. For use of the liner in expedition boots, as Polar A/P/S or Polar Advance, we recommend you choose the expedition boots 2 sizes larger than the liner for a good fit. Polar Liner can be heat moulded. This should be done by a specialist in heat moulding.