TLS is a thermal insulation lining system which uses layers of Thinsulate® to completely surround the foot without cold spots. The Thinsulate® lining is fixed in place with minimal use of adhesives to maximize the loft and warmth of the lining. The floor of the boot is also insulated with a triple Thinsulate® layer to insulate the floor of the boot from conductive heat loss to the ground, especially important when crampons are fitted. This full Thinsulate® lining which extends underfoot gives Boreal mountain boots a significant warmth advantage.