Stainless grade, wall thickness, and whether it is rigid or flexible
A liner is the stainless tube that goes inside a masonry chimney, either because the masonry is no longer sound or because a modern appliance needs a smaller cross-section than the flue it inherits. Four figures decide and all four are published by the serious makers. The steel grade comes first: 1.4301, 1.4404 and 1.4571 appear across this shelf, and the differences are about resistance to condensate rather than to heat — a liner on a modern low-temperature appliance spends its life wet in a way an old open fire never did. The wall thickness, in tenths of a millimetre, is the figure that separates a liner meant to last from one meant to pass an inspection; 0,6 mm and 1,0 mm both exist here. The internal diameter must match what the appliance needs, and matching it to the appliance rather than to the old flue is the whole reason for lining. Then rigid or flexible: rigid sections are made for straight runs and joint into each other, flexible tube goes round the bends an old chimney has, and the flexible one loses draught to its own corrugation — a real effect that listings never quantify. Finally the temperature and pressure class the maker declares, which is the shorthand for what the tube is certified to carry. We compare type, diameters, material thickness, steels, insulation, standard, approval and fuels.
Ø 120/180 mm, 500 mm, 0.6 mm wall, 30–35 mm mineral wool, inner 1.4404 / outer 1.4301
Half a metre of twin-wall with 30–35 mm of mineral wool, acid-resistant 1.4404 inside and 1.4301 outside.
Best for: Extending or repairing an existing 120/180 twin-wall run whose system is already known
Inner AISI 316 / outer AISI 304, 0.6 mm, 25 mm rock wool ≥ 90 kg/m³, 500 mm overall / 452 mm useful
The only listing here to publish its useful length beside its overall length — and the only one to print what must never be done to it.
Best for: A buyer who wants to know exactly what the component is, what it is not for, and how much of it is actually chimney
Complete kit DW 150, 4.5 m, 0.5 mm inner wall, 30 mm mineral wool, 600 °C continuous, DoP 0432-CPR-00403-10
Four and a half metres with a declaration of performance number, 600 °C continuous, and the free-standing height stated.
Best for: A tall external run where the top three metres are unsupported and that has to be planned
45° element, Ø 150 mm inner, 25 mm insulation, 0.5 mm, inner 1.4521 / outer 1.4301, corrosion class V2
A 45-degree element for building an offset, with a corrosion class stated and a sealed insulation that cannot take damp.
Best for: An offset in an existing New Line run, where a chimney has to step around a soffit or a beam
Complete kit, Ø 150/200 mm, 0.5 mm, 25 mm insulation, V2A and V4A, DIN EN 1856-1:2009-09, class V2
A complete kit with a twist-lock joint, tested to DIN EN 1856-1 and stated fittable by somebody with no previous experience.
Best for: A new external chimney where the kit can be configured to the wall before it is ordered
Complete kit, Ø 150/210 mm, 3.3 m, 50 mm wall spacing, push-fit twin-wall
A 3.3-metre kit at 50 mm wall spacing — and the only listing on this shelf that says outright its parts fit nothing else.
Best for: A complete new run of exactly this system, ordered as one kit with nothing mixed in
Ø 150 inner / 200 outer, 500 mm, V4A inner, 25 mm mineral insulation, clamp included, to 600 °C
A half-metre element that names the two systems it fits — and comes with its clamping band and a twenty-five year warranty.
Best for: Extending an existing run of one of the two named systems, with the clamp already in the box
Complete kit DN 120, 3.7 m stretched, 0.5 mm wall, 30 mm insulation, soot-fire safe to 1,000 °C
Soot-fire safe to 1,000 °C, with all the clamping bands included — and the clearest list of what it must not be used for.
Best for: A wood appliance on natural draught, where a flue that excludes coal is the right specification
Only the specifications at least four models out of five state. A column that is more empty than full compares nothing.
| Model | Price | Amazon reference | Approval | Diameters | Fuels |
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Specifications: manufacturer sheets and Amazon product pages. Prices and availability: Keepa. No product on this site has been physically tested.
Most recent revision in this category: September 22, 2026.
