FOR SMALLER THAN 5/8" O.D. HOSE: Rule of thumb next size larger for ferrule and clamp.
FOR LARGER THAN 5/8" O.D. HOSE: Normally there is sufficient play built into clamp or ferrule to allow for clamp and ferrule to fit properly when same size is ordered.
Oetiker Number - 13.3
Nominal Size - 1/2"
Clamp Index - E