This is a 10mm endpin socket for cello made by Bogaro & Clemente. The body is made of blackwood. The black rod in the photo was attached as a test for fixing the screw and is not included with the product. I purchased this but was unable to use it because the size did not fit the hole in my instrument, so I am reluctantly selling it. Normal endpin sockets fix the endpin with a single screw, but this item has a relatively unusual structure that holds the endpin with a wide ring-shaped part. (It's similar to the picture from Sasaki Violin Workshop: https://www.sasakivn.com/werkstatt/qa/stachelwechsel2.gif) The socket has a diagonal taper, and the maximum diameter of the side to be inserted into the instrument is 24.6mm (measured with calipers). Although it is a socket of a general size, please note that it cannot be installed if the hole diameter of the cello is different. I use the same type of endpin socket, and it has the following features: * The pressure on the endpin is reduced, and the surface of the rod is less likely to be scratched. * Because the endpin is held over a surface rather than a point, it feels more stable, and the sound quality becomes more solid. That's all. Thank you.