Sigvaris 503C Series Natural Rubber: 30-40 mmHg Open Toe Knee High Compression Stockings for Women and Men. The Most Therapeutic Support Hose. Proven efficacy through numerous scientific studies. Designed with a low fatigue rate to sustain compression throughout the day. Ideal for patients with more serious indications or long-term therapy. Unisex. Manufactured from double-covered, soft, natural rubber to offer the greatest degree of elasticity and great durability. New Precise Fit Sizing. A newly-developed sizing chart for the Natural Rubber Series accommodates larger ankle circumferences up to 18" (40-46cm). Easy Wear. The high-stretch knit construction in combination with double-covered yarns provides great elasticity and easy donning and removal. Fiber content: 70% nylon / 30% natural latex rubber.