Dual Action Pneumatic Air Cylinder

[metric_taper]

The 4 way, has 4 ports, air inlet, air outlet (common when exhausting either the A, or B port), and the A, B (or 1,2) ports to the double acting cylinder.
A 5 way, make the outlet ports separate between the A, B connections. The intent is to put an air restrictor in them and control how fast the cylinder moves, and you can have a different rate between the 2 cylinder positions. One example of this is a door opener, that opens fast, and closes slow.
The 5 way will probably cost more, but if you already have one cheaper then a 4 way, that's the way to go.