The Rice barrel site lists the reading profiles, breech, length( 40 15/16 ) and calibers available. The nice thing about this barrel is the rate of taper. It is similar to the early transitional, but a smaller muzzle. I have measured several original early barrels, and they all seem to be within this rate of taper. Not all have the muzzle dimentions, some smaller, but the Reading muzzle allows for a lower front sight because of the muzzle size. The transitional barrel in 1 1/16 breech has a muzzle that is almost .05/side larger than the 1 1/16 breech reading....WOW...thats huge!! The straight section is only .02/side larger...not a big deal there, but the smaller muzzle along with the taper of the breech is what makes this barrel so great.