NOT ADVISED FOR WIDE CALF: Boot opening measures approximately 15" around. Flat Heel: You may feel like wearing yoga socks. We advise inserting Arch Support Insoles for better comfort and protection. Adjustable Collar: Secure tie at the top prevents water dropping into the boot. Ultra Lightweight: Each pair weights approx. 2 lb, won't feel tired when wearing them, even for a long-time working. Super Soft: Made of highly flexible rubber material, easy folded and packed in small bags. PS: If there were any unpleasant creases on the shoes, use a hair dryer or an iron to get the wrinkles away. Rubber sole.