This is a special item for enthusiasts. I once considered rebuilding the F rotor of a Yamaha custom trombone (such as the 8420 or 8425 series) into a Conn-style wrap, similar to the 648 or 643 models. To do this, I docked a 648 rotary valve with the joint of an 8425G2. However, I was unable to obtain new F rotor parts for the 648, so the plan stalled and my passion cooled. Please use it in my stead. These are rare parts from discontinued models. You can either convert the F rotor of a custom series to a Conn wrap, or change the rotary valve of a 648 or 643 from a string-pull to a ball-joint system. This is truly for enthusiasts. To adapt the 648 rotary valve, which was originally string-pull, to a ball-joint system, I used a rotary rotor plate for a Xeno model and re-drilled screw holes in the rotary casing to attach the damper rubber base, rotating it 180 degrees. The original screw holes were plugged by inserting screws from the inside of the casing. Please check photos 4 and 5. The lever is not included, but I believe a current Xeno lever would likely be a direct fit. I have attached a Xeno rotary cap.