We bought this so we could to professional-quality spark plug terminals but this does even more than that.  This kit includes three different interchangeable die sets:  One for spark plug terminals, one for standard 22-10 AWG disconnects (ring terminals, spade terminals, etc.) and a third set for finer non-insulated terminals (Metri Pack, Weather Pack.)  It does a great job on the first two.  For crimping Weather Pack and Metri Pack terminals, we prefer the 533 Crimper.