I bought a nite sight that said it was for a JFrame. The width of the blade is .125. Which is hair wider than than the stock blade. I filed it on both sides till it fit in the grove and then had to round the blade to get it flush. I drilled the hole and pinned it. It came out good. Only error was I scratched the side of the site on one side but for now I just blacked it out with a marker. So in theory any sight that says it will fit a Jframe or a ruger sp101 should be made to work on the 856. I think the actual width of the blade is .117 or .118 approx. I got that number from a guy with an 856 Defender. They come with a bitchen night site and Im sure it fits our 2 inch barrel but Taurus says it wont. I tried to buy one from Taurus but they gave me a hard time. I said just sell it to me. She said if I modify my gun it will void the warrenty,!then She said they are on back order and took my credit card number. I guess I hv one on backorder. Not sure she probably just did that to get rid of me. Here are some pics.