The present invention provides an apparatus for molding a material such as plastic. The apparatus includes a mold body, a first plurality of ribs, and a second plurality of ribs. The mold body includes a molding skin of substantially uniform thickness having a first surface and a second surface. The first surface is adapted to mold a part. The second surface is opposite the first surface. The first plurality of ribs extend from the second surface. A plurality of thermal conduction surfaces are defined on the second surface between the first plurality of ribs. The second plurality of ribs are interleaved with the first plurality of ribs. The second plurality of ribs include end surfaces displaced a substantially uniform distance from the plurality of thermal conduction surfaces to define a plurality of fluid flow conduits adapted to contain a coolant.