Hello, this is a used blued HK P2000 model 40 caliber barrel with guide rod assembly. Barrel length is 3.66 which is standard size and will not fit any other make, model, or caliber. Bore and rifling both look pretty decent overall. Please see pics for more details. Any questions, feel free to ask. I do my part to get the item to you quickly but I do not, obviously control the speed at which the carrier delivers it. So if your item is late please have some patience, thank you.