Dormer PFX premium cobalt HSS drills are available in screw machine, jobber, taper and extra-length designs. Providing options for drilling applications, the PFX is ideal for most engineering materials drilling 3 diameters deep (A920, A921), 6 diameters deep (A900, A901), 10 diameters deep (A940, A941) and 15 diameters deep (A976, A977, A978).