Shotgun choke constriction is marked on band so there is no need to remove choke to verify size. Shotgun choke constriction from Cylinder to Extra Full, in .005 inches (.127mm) increments let you precisely match your load to the shooting conditions. Long tube extends beyond the length of the muzzle, features highly polished interior for less pellet deformation; reduced fliers and tighter patterns. Knurled grasping band speeds installation and removal. Shotgun choke constrictions is marked on band so there is no need to remove choke to verify size. Helical rifled Diffusion spreader tubes provide a pattern that is more open than cylinder. It is not recommended to shoot Federal's Black Cloud or any of their ammunition that utilizes their Flight Control Wad in ported chokes due to interference with its performance. Please note, you can shoot steel through our 17-4, stainless steel chokes, Cylinder through Improved Modified only.