The present invention relates to an end cap for capping an end of an extrusion of a printhead assembly. The extrusion defines a plurality of respective channels for each carrying a medium such as air or ink and each channel has an opening at the end. The end cap comprises a body and a plurality of protrusions which extend from the body. The protrusions are located so as to each correspond with a respective channel opening. During capping, the body is located so that each protrusion is inserted into a corresponding channel opening to thereby plug each channel and cap the end of the extrusion. A print head assembly comprising an extrusion which is capped at an end with the end cap is also provided.