Available sizes: 6 8 10 12 14 16 Chrome Ferrules Only FERRULE SIZE ON THIS ARM IS APPROX. 25MM PLEASE TAKE THIS INTO ACCOUNT WHEN ORDERING THIS FOR EXISTING BOBECHES OR WHEN ORDERING NEW BOBECHES. IN ORDER FOR THIS ARM TO FIT BOBECHE THE BOBECHE MUST HAVE AT LEAST A 1-1/8 CENTER HOLE. WE CAN DRILL OUR BOBECHES TO ACCOMODATE BUT YOU MUST REQUEST US TO DO SO.