I have used these on three Rugers, a 6" Security Six .357, a Super Blackhawk .44 Mag. and an Old Army black powder.
If you are past age 50 and have trouble seeing open sights, and use longer barrels of 6" or more they will help. I did not find them helpful for shorter barrel revolvers for combat style shooting.
A potential disadvantage is that the center of the aperture is higher than the original rear notch and you may not have adequate range of adjustment to lower the rear sight to obtain a proper zero before the sight bottoms out. This isn't a problem if using 125-gr. or lighter bullets in the .357 where you need to crank in more elevation anyway, but is a problem with the .44 and larger bores if shooting bullets over 200 grains.
On the two guns where I wanted to keep the ragged hole sights I had a gunsmith machine some off the bottom of the adjustable rear sight and also deepened the bottom of the sight cut in the frame so that I could lower the sight body as much as possible and still clear the hammer nose.
