Please see the photos for accurate measurements. 

Ventilator Cowl Adaptor To Fit Twin Wall Pipe for Wood Burning Stoves

This adaptor is essential for connecting spinning ventilator cowl and twin wall pipe together safely, correctly and securely when installing a wood burning/multifuel stove.

Inside Diameter: 6"/ 150mm

Outside Diameter:200mm/ 8" 

You will get what you see in the photos. NO fixing comes with it. 

This is a  heavy duty Stainless Steel Connector .