A choice of 2 hose clamps depending on your coolant hose size:
 
Hose Clamp for standard 16mm (5/8") ID coolant hose:
Clamp range: 20.5 - 24.5mm OD (16mm coolant hose is 23mm OD)
 
Hose Clamp for standard 19mm ID coolant hose:
Clamp range: 26.1 - 30.2mm OD (19mm coolant hose is 27mm OD)