Stove Fitter's Warehouse offer a full Twin Wall Design Service with all designs prepared within our Twin Wall Design Studio. Contact us for further details (firstname.lastname@example.org).
Duraflue Twin Wall was launched to the market during 2014 and, due to its high quality and innovative design, is already a favourite amongst professional stove fitters.
If you require the part that "pokes into the house" to be black rather than silver (so you end up with "all black in house") then you can. But you have to buy this full item and remove the bottom section of the snout. You will then buy a black adjustable length and remove its snout to use on your 135 degree t.
Why not just mix a standard silver 135 degree T (non-adjustable) with a standard length of black twin wall? You can but you end up with a locking band half in the property and half out of the property. This locking band is always in the way, especially if fitting a finishing plate.