A sole structure having a ground-facing surface and an upper-facing surface, the sole structure comprising: a sole member made from one or more parts and including a base surface , a medial side , and a lateral side , wherein the sole member includes a first sole part and a projection field engaged with or integrally formed with the first sole part, wherein the projection field comprises a plurality of projections that extend beyond the base surface and have exposed free ends , wherein the plurality of projections includes at least 20 projections having a projection packing density of at least 0.62 projections per square centimeter (4 projections per square inch) in the projection field , wherein a first subset of the plurality of projections have a length of at least 5 mm, and wherein at least a majority of the plurality of projections in the projection field readily bend under force applied by weight of a user of the sole structure ; wherein the projection field includes a projection field base having a first surface and a second surface opposite the first surface , and wherein the plurality of projections originate at the second surface and extend from the projection field base in a direction away from the first surface and the second surface ; wherein the base surface of the sole member includes an interior surface and an exterior surface opposite the interior surface , wherein the base surface has an opening defined through it that extends completely from the interior surface to the exterior surface , wherein the second surface of the projection field base is engaged with the interior surface of the base surface , and wherein the plurality of projections extend through the opening . a sole member made from one or more parts and including a base surface , a medial side , and a lateral side , wherein the sole member includes a first sole part and a projection field engaged with or integrally formed with the first sole part, wherein the projection field comprises a plurality of projections that extend beyond the base surface and have exposed free ends , wherein the plurality of projections includes at least 20 projections having a projection packing density of at least 0.62 projections per square centimeter (4 projections per square inch) in the projection field , wherein a first subset of the plurality of projections have a length of at least 5 mm, and wherein at least a majority of the plurality of projections in the projection field readily bend under force applied by weight of a user of the sole structure ; wherein the projection field includes a projection field base having a first surface and a second surface opposite the first surface , and wherein the plurality of projections originate at the second surface and extend from the projection field base in a direction away from the first surface and the second surface ; wherein the base surface of the sole member includes an interior surface and an exterior surface opposite the interior surface , wherein the base surface has an opening defined through it that extends completely from the interior surface to the exterior surface , wherein the second surface of the projection field base is engaged with the interior surface of the base surface , and wherein the plurality of projections extend through the opening . <EOS>