Please note that CPM M4 is not a stainless steel and while the blade is coated for protection, the ground edge and laser markings must be properly cared for to prevent rust. The coating is black Diamond-Like Carbon (DLC) with a semi-matte Tumbled Finish. DLC is a very thin (1.5 2 microns) but highly abrasion resistant coating that is bonded to the metal by physical vapor deposition (PVD) under vacuum. DLC is a much more abrasion resistant coating than the BK1 black coating used on the CPM S30V stainless steel blade of the standard RSK® Mk1.