Heat Holders Ladies Thermal Tights Black. Lock in the heat with the Heat Holders Ladies Thermal Tights. Presenting the perfect under layer, the Thermal Tights helps lock in the heat with a rating of 0.52 TOG. Made from advanced insulating yarn with a super soft brushed inner to help lock in the heat, the Thermal Tights offer a light stretch for added flexibility whilst the elasticated waistband and gusset panel provides a better fit and added comfort all day long.