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Spandex provides support in the instep and arch area. Low-density pad cushions instep from lace pressure. Medium-density pads protect against shock, abrasion and blisters.Protection Level 3Made of 77% Foot-Health acrylic, 16% stretch nylon, and 7% spandex.Approx. Length: S(8 in.), M(9 in.), L(11 in.), XL(13 in.).Avg wt. 3.5 oz.Made in USA.Thor Lo's Protection LevelsThree simple level designations will help you to pick the Thor Los that are right for your activity. Both thickness and density (padding) have been taken into consideration when assigning Level of Protection to each Thor Los style. Each style features padding engineered to protect your feet for the intended usage.Protection Level 3 - Maximum protection for the most rugged and challenging activites and weather conditions.Protection Level 2 - Moderate protection for those activites that are somewhat strenuous but are not of long duration.Protection Level 1 - Minimum protection for those activities that range from casual/leisure to 'walks in the park'.