The only choice for Ultimate Thermal Performance These super warm, super cosy Heat Holders thermal leggings have a soft brushed inside, which maximises the amount of warm air held close to the skin. Wear out and about this winter for warm legs! These leggings are made from an advanced insulating yarn that provides high performance insulation against the cold. They also feature a comfort gusset which improves fit and adds comfort for all-day wear. These Leggings have a TOG rating of 0.52! What does ‘TOG RATING’ mean? Well, TOG is a recognised measure of a textile’s thermal ability. Simply put, the higher the TOG rating, the better a products is able to keep you warm.