Meprolite offers two styles of front sight for the S&W K and L frame revolvers.
One replaces just the red front sight insert, but retains the same overall front sight height. Obviously, this requires a front sight with an insert, but it does not require a removable front sight. It looks a little different...
The other style replaces the entire front sight. It also retains the same overall front sight height. It obviously requires a pinned front sight that can be removed.
I opted for the latter on my 686+.
It gives it a little different look, which isn't bad, just different. The sight works great and the sight picture is better than the original in terms of having just a bit more space between rear sight ears and the front sight blade.
The three dot effect is fine at night, but if you're like me and prefer a black on black right picture during the day, just take a black sharpie and color over the white dots. That will give you an all black sight during the day, but in low light, the tritium dots still shine brightly through the thin layer of ink.
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Installation isn't hard, but requires some basic tools and basic tool skills. You'll have to remove the locking collar from your original rear sight blade and then install the new rear sight blade and collar. The collar is held in place by the hollow end of the sear sight screw which is was punched and expanded at the factory to secure it. That normally means drilling it out to remove the collar.
My sight set did not come with a detent pin and spring, and the original S&W was bigger than the hole in the Meprolite rear sight. But a number 50 bit (.070") was a slip fit in the original hole and worked fine to enlarge the hole in the Meprolite sight so the old detent and spring could be use.
Snug up the new collar and double check to make sure it a) move freely, but b) has no slack in it, so that the rear sight adjusts easily, but doesn't have any lateral play. There's a sweet spot, you just have to have a light touch to find it.
The original front sight will need to have pin removed with a small punch so that you can remove the old sight, then drill the new sight for the pin. Again, it's not hard if you have some basic tool skills and some attention to detail.
The old sight will probably be stuck in the groove, but a light tap with brass hammer will break it loose. Use a brass punch placed on the front of the sight so you don't hit the muzzle with the hammer.
A rubber padded clamp can be used to hold the new front sight in place while you drill the hole. I drilled it only part way to mark the position and then finished on a drill press to ensure it was square. If you don't have a drill press you can drill it 1/2 to 3/4 the way through from one side free hand, taking care to drill as square as possible, and then finish the hole from the other side so the pin will go through smoothly. A number 55 drill bit worked fine.