For small children and babies. Duck shoes are suitable for use by children with motor problems, perception problems, weak propulsion, muscular hypotony, pigeon toes, growth problems as a result of a developmental delay, to name just a few. The flippers have a complete shoe which holds the foot. Smaller feet (approx. from size 18) can wear crawling socks. If you turn up the edge of the sock around the heel of the flippers, the feet have perfect hold at this size.