Patternmaster extended chokes are designed to be used with the 3 1/2" shells for maximum pattern and density. The difference between the Patternmaster Extended chokes and Patternmaster Standard/Long Range is the length. Patternmaster concept is that the "studs" inside the choke grabs the base of the wad as it passes through while the front of the wad is flush with the front of the tube. Since the wad is longer in the 3 1/2" shells we have made the tube longer to maintain a tight, dense pattern. Remington chokes fit popular models such as: Remington 870 Remington 887 Remington 11-87 Remington 1100 Remington V3