They appear to be replaceable, but I'm not going to. They come in real handy in the woods and low light conditions, plus me eyes can see them a little better. I have been using it on the trap lines and it really puts a hurtin on some coyotes. I down loaded some .357mag 158gr sjsp to arround 1050-1100fps for it (inbetween 38+p and .357 loads), and it a pleasure to shoot
. When trapping season ends I will work on the loads, but this one seems to be plenty out of that little gun.
In a pancake holster and walking through the woods and in and out of the truck all day I hardly even know its there other than the comfort of (KNOWING) its there when I need it.