Just wanted to add a little to what I said earlier. I was on my phone so I couldnt write too much. Jester is spot on with those dimensions. In addition to that I have found that a stepped barrel from 7/8 to 3/4 to 5/8 will play differently than 7/8 to 5/8. Depending on the gut you may want to use one over the other. I have had the best luck with 7/8 to 5/8 on Wade's SR-1 gut, while another gut from Wade sounds like crap and is harder than heck to blow with this same dimension. For that gut, I use similar to what Jester described. Then there is the question of how long is the 5/8 portion. This will also change the playability of the call. I have found that the closer you get the 5/8 to the tip of the gut the more responsive the call is, but you lose some forgiveness in the break over point. Conversly, the farther away you are allows for more forgiveness but less responsiveness. Then the sound can be affected by how you tune the call along with the length of the call, both insert and barrel. In tunning, the closer to the tip of the reed you place the wedge, the higher pitch the call will be and it may require more shaving. Placing the wedge farther away from the tip will give a lower pitch, but will not handle a lot of shaving. All of these aspects will play a role in the over all sound and playability of the call, at least that's what I have found. That is about all I know on the subject. Beyond that and I am lost. There are a lot of guys on here that are much more knowledgable than I am.