Works with Flexfab 
5526-031 5/16" Silicone Heater Hose
5526-025 1/4" Silicone Heater Hose

These are custom made clamps for small sized heater hose. 
These are lined so the hose will not extrude these are the only clamps we recommend for Silicone heater Hose.
They don't have a size range because they are made specifically for the 1/4" and 5/16" Heater Hose.

Flexfab
Size: #4
Material:
Stainless Steel
Qty: 10 pcs

Lined Worm Gear Clamps
Recommended for Silicone Coolant and Heater Hoses

Specifications: 
• All 300-grade stainless steel lined worm gear clamps
• Hex Head: 5/16” 
• Band Width: 9/16”
• Resists salt water and may be used in marine applications
Applications:
• Recommended for silicone coolant hose, heater hose, marine, and silicone tubing