- Size: 39 • Outer material: polyester and spandex, providing a comfortable feel and allowing for easy on and off. • Inner material: synthetic, flexible, and soft. The elastic material makes folding easy, and the elastic collar allows for easy use. • Rubber sole: non-slip and durable, ideal for various activities such as fitness, yoga, pilates, spa, relaxation, beach, water park, and hiking. • Flat heel: lightweight and flexible, protects your feet from stones, shells, and other sharp objects. • Slip-on design: provides unobstructed comfort. • Product measurements: 5 cm wide, 5 cm high, and 16 cm long.