They have both a FL and a collet. The other 2 dies are a seater and a crimp die.
They're not usually 2X the price of a 3 die set. 48$ for 3 dies set and 74$ for 4 dies set. If you plan on using both the FL and the collet it's a good deal. Otherwise either the 2 dies collet set or the 3 dies are ok, depending on your needs.
If the 4 dies set had been available for my calibre it's what I would have bought.