yes, a restrictor plate that reduces the airflow through the core. Some listmembers have removed it (to get more heat), others claim it should be left in place.

alistair

On 2013-01-21, at 8:03 PM, Mike South wrote:

> I noticed this some time shortly after we took out my heater box to replace
> the core:
> *
> 
> http://tinyurl.com/b7h7d5n*
> *
> *
> Is it part of the heater box?  Where does it go?
> 
> mike