Heater Block Insulation
Credit where credit is due, I saw Brooke Drumm use this on his hoteneds.
It's something used in the aviation industry and it's called 'firesleeve'.
You can just buy some and cut it to size. (Why is this not more pupular?) Ours is 16mm/ 10mm ID.
- 10 mm ID here - specified by ID - https://www.amazon.com/Heat-Shielded-Sleeve-Lines-Electrical-Wiring/dp/B015S664EQ?th=1