Golf club head having supported striking face

An iron type golf club head, comprising:

• a striking face having a substantially flat outermost surface, and having a lower leading edge and an opposite upper topline edge;
• a top portion extending rearward from the upper topline edge;
• a sole extending rearward from the lower leading edge;
• a support bar protruding rearwardly from the striking face and extending in a toe-heel direction of the golf club head;
• an intermediate wall extending between the sole and the support bar;
• and
• a front cavity defined at least in part by the striking face, the intermediate wall, the support bar, and the sole,
• wherein, when the golf club head is in an address position on a ground plane, a greatest cavity height distance in a cross-sectional plane, as measured along a first direction perpendicular to the ground plane and from the ground plane to a top of the front cavity closest to the top portion is less than 70% of a greatest club height distance in the cross-sectional plane, as measured along the first direction and from the ground plane to the top portion, wherein the cross-sectional plane is perpendicular to the ground plane and taken at Face Center,
• wherein a sole slot is defined at least partly in the sole and exposes the front cavity to an exterior of the golf club head,
• wherein the sole slot is at least partially filled with a first polymer material,
• wherein a top slot is defined at least partly in the support bar and exposes the front cavity to the exterior of the golf club head, and
• wherein the top slot is at least partially filled with the first polymer material or a second polymer material different from the first polymer material.