Are you referring to the one that you mount to the cue itself?
and then cut a NEW ferrule from the existing shaft?
I've used one of those. It served its purpose, but I didn't like the idea of shortening the cue by 2 inches.
best to cut off old tenon. face new shoulder. bore 5/16 hole into shaft aprox 1 1/2 inches and epoxy new piece of maple in. obviously you need a lathe to do this. also start with smaller bit and work your way up or you might split out the shaft.