Replace if the head is warped or cracked. Many times a leak occurs because of a hairline fracture. To be sure, spray a soapy water solution around the head and if you see bubbles, this is where the leak is. Always replace gaskets when installing a new head, and remove (and sand) the head of any old gasket material.
This item fits the following models:
3-Nailer Combo Kit w/ Accessories
3-Nailer Combo Kit
1/4" x 50 Ft Noodle Air Hose with Coupler and Plug