 So I'm Dr. Elisbovero, I'm working at Oxford University at the Cadilly Research Center on the reconstruction of the manufacturing techniques of early Islamic crystal. And so for doing that, we're doing long older type of research, experimental archaeology. So for this, a wood turner reconstructed for us two types of ball lathe. So this first model, which is movable, we can remove this part of the ball lathe. So it's made after the examples still in use nowadays in India. And so you can attach different types of drill bits and so on to this type of ball lathe. But more recently, and I think this one is more useful for early Islamic periods, this is a replica of a ball lathe which is on the picture in the album of the Emperor Shangir, so which dates off the beginning of the 17th century. So this is almost the exact replica. So this is the same thing, you know this part is removable and can attach the different type of drill bits and different tools that you're going to use to carve the rock crystal. So let's start with the beginning of the process. So first you have to sew the big block of rock crystal that you have to shape it in the rough, you know, form that you need. And actually rock crystal is a hard stone of course, but it's also extremely brittle. So you cannot work it, shape it or drill it or hollow it out and so on, using the percussive tool, the hammer and point that the structure would do, for instance, for marble. Because it would shatter. Yeah, of course. So for that, you are going to work and since the neolithic they use the same technique, it's abrasion. Okay. This is based on the same principle, abrasion.