An article of footwear may include a sole structure comprising an outer member and a plurality of ground engaging members, including a first ground engaging member. The ground engaging members extend substantially downward from the outer surface of a sole structure. Ground engaging members, or cleats, may be auxetic structures that can increase their dimensions in a direction that is orthogonal to the direction of applied force or tension. The ground engaging members may comprise a series of faces joined along hinge portions that allow ground engaging members to flatten and expand significantly. The first ground engaging member may have a substantially three-pointed star-shaped pyramidal structure. The outer member may have a more elastic material than the material comprising the faces of ground engaging member. The outer member may have an inner surface with apertures that correspond with the ground engaging members of the outer surface.