The Shieldmaster straight wall sleeve fits around your pipe when passing through a wall to protect your wall from the heat generated by the flue pipe.
Shieldmaster does not need any additional silicone or sealants to seal the joints. It has a unique push-fit locking system to make connecting and disconnecting really simple.
Please note - as with all twin wall parts the diameter quoted is the internal diameter - the external diameter is 2 inches larger due to the surrounding insulation.