I have some Beeman ICS hunters that I have really liked. 2018's are too thin, I picked up a broken 2019 at a shoot, fits but a bit loose, I had a 21? that I used with my cx 150s and fit perfectly, way too loose foe the beemans. My footed arrow took a wicked hit on live maple and the footing bulged at the point. I don't know if I could have gotten a better fit or not. I might have to search for a 2020 or thicker wall. That should decrease the internal diameter, but I don't know. Just my experience.