In one example, a printhead structure includes: a first layer; an array of openings in the first layer to form printing fluid ejection chambers; a second layer on the first layer; an array of orifices through the second layer, each orifice located adjacent to one of the openings in the first layer; a groove in the first layer spanning substantially a full length of the array of openings; and multiple holes through the second layer to the groove in the first layer.