CN81204 Aftermarket Piston Driver For Max CN70 Coil Nailer. Mechanically locked piston driver interface. This professional piston drive is for MAX CN70 coil nailer. Heat treated S7 steel at the tip of the piston to Rockwell hardness of 55~56. The cap end is at about 52. The piston driver cap is made of Aerospace Aluminum grade 7075. A brand-new, unused, unopened, undamaged item in its original packaging.