Yep, that's a standard size 20. No extended slot on the receiver and no buffer inside either, but the X is the key. Matter of taste, but I hate those old Cutts style choke systems. They do work. I remember when they were all the rage on the Skeet fields. The internal choke tube systems pretty well killed off the old bulbous looking choke systems. If you decide to go shopping for a replacement barrel, get ready for sticker shock.