I'm going to sell my Cylinder and Slide Extreme Duty Sight. This is the same type of sight that Smith uses on the new night guard line of revolvers.
I am selling it because it is not adjustable and shoots too low for my 3 7/8" gun with my fiber optic sight. I suspect it will work fine for a 4" or 5" gun. It will work on a K, L, or N frame gun with the "newer" style rounded rear sight (compare with yours).
Looks like this, and actual picture below. I can get more pictures.
New, they cost $82 plus shipping. Sell for $75 shipped.