Yes, there are epoxied in place. There is a hold underneath that fits over your existing bead to center the new one. In my case, the original bead was mounted off centre so I had to take it off.
My first attempt I had at mounting the XS sight was with the original bead in place and it had groups landing well to the right. I had JB Welded it in place which sounds bad. In fact it came off by applying heat with the tip of a soldering iron inside the barrel so as not to mar the finish.
After getting it off, I removed the original bead and simply eyeballed the new XS sight for having it at top dead centre and it worked. The JB Weld has held up well and it has been on for months now. It is a very nice sight and XS shipped directly to me.