What is the duvet made of, will it keep me from over-heating?

The outer cover of the Simba Hybrid® Duvet is made from 100% breathable cotton.

On one side, Stratos® temperature-regulating technology is applied to the fabric (it's the side with the blue piping). Stratos® was inspired by the technology developed to keep astronauts a stable temperature throughout the extremes of space travel; for you, it will absorb heat when your temperature naturally rises during the night, storing it to release back to you when you cool down again. And the hypoallergenic fibre fill is also enriched with semi-conducting minerals that dissipate heat.

So whether you run hot or cold, the Simba Hybrid® Duvet has you covered.