The Nature Flex Technology™ features a flexible rubber sole that allows toddler to feel the ground under his or her feet. This technology and design ensure that the shoes are not overly rigid, and allow the foot bend naturally with each step, improving ankle strength and balance. This is as close as a baby can get that barefoot feeling, while still having the protection needed when playing outside. Wobbly Waddlers rubber soles also ensure better grip on any slippery surfaces.