What is the difference between a Dopper Insulated and a Dopper Steel?

The Dopper Insulated has an insulated double wall to keep your drinks cold or warm.
The Dopper Steel has a single wall. This wall has the same temperature as your drinks; not a good idea with some fresh made tea.

 

The Dopper Insulated keeps your cold drink cold for 24 hours and your hot drink warm for 9 hours.