frogplus are Cressy patented technology made of 3 materials in the injection molding process in mind. This three kinds of materials are each: Socks with a pretty and comfortable piece of elastic materials, webbed side notch; 2 ND species you are stretched to the will of the webbed side and our metals are a revolutionary new technology of double density polymer; after the first, mumps, silicone material, and both together to form a channel effect.