Just a matter of clarification, but you don't "install" extended chokes. You thread the barrels for screw in choke tubes, then you can use either flush or extended tubes. All aftermarket choke manufacturers have extended chokes to match a multitude of thread systems.
Great point Stan. Briley will thread your barrels for their thinwall chokes, and you can then interchange either flush or extended. You buy whatever combinations of the two you want. Important info because SC shooters don't hold the sxs up to the scrutuny of aesthetics like the traditional purists do, so Mark won't be looked on with aspersion on the SC course as in the field with the hard liners, lol.
JR