air brick installation

[hairyfingers]

Hi

I need to install another air brick to aid ventilation to the underfloor void. It's a daft question but having bought the external air brick what do I use to channel the airflow through the cavity and through the inner block

thanks

 

[Alastairreid]

http://discountbuild.co.uk/hepworth-cavity-liner-200-x-215-x-65mm?gclid=CIqG0s7YiLwCFYrjwgodCHMASw

 

[hairyfingers]

Perfect. Thanks pal.