Improved cylinder would be a looser choke. One step looser than Modified. Basically means that the pattern will open up faster than a Modified and less than a Cylinder choke. Best bet is to pattern the shotgun with the load you intend to use and see what happens. It would be considered more of a close pattern say 25 to 40 yards depending on the shot and powder charge. Only way to really know is to pattern the shotgun with the load in hand.
