Caterpillar Men's Flame Resistant Work Sock 100% Other Fibers Made in US Machine Wash FR Certified to NFPA 70E , CAT 1, ATPV 5.2 6.2 oz FR 98% merino FR (55 percent rayon/33 percent/12 percent nylon) 2% elastic Machine wash Moisture wicking, breathable, anti-odor Over the calf construction Rib knit construction for optimum stretch and recovery