PTFE tubes: Capricorn sizes, heat limits and when to replace

Short answer

Capricorn makes two bores sized for 1.75 mm filament: TL at 2.05 mm and XS at 1.90 mm, both 3.95 mm outside. Capricorn does not recommend printing above 260 °C with TL. Replace any tube that is deformed or worn, and buy Capricorn only from Capricorn or its resellers: it says neither sells on AliExpress or Alibaba.

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Where PTFE sits in a printer

A PTFE tube guides filament with little friction. You find it in three places:

• The Bowden path: the long tube from a frame-mounted extruder to the hotend on a Bowden printer.
• Inside the hotend: some hotends line the heat break with PTFE down toward the nozzle. ELEGOO says the Neptune 3 Pro, Plus and Max hotend has embedded PTFE tubing.^[1]
• Feed and guide tubes: Prusa says the MINI and MINI+ have four PTFE tubes, two external and two internal.^[2]

A tube inside the hot zone sees much more heat than a feed tube, so the heat limits below matter most there.

Capricorn TL vs XS

Capricorn specifies its TL tubing at 2.05 ± 0.05 mm inner diameter and its XS tubing at 1.90 ± 0.05 mm, both with a 3.95 ± 0.05 mm outer diameter.^[3]

Capricorn tube	Inner diameter	Outer diameter
TL	2.05 ± 0.05 mm	3.95 ± 0.05 mm
XS	1.90 ± 0.05 mm	3.95 ± 0.05 mm

The outer diameter is what your push-fit couplers grip, so both fit the same fittings. The tighter XS bore leaves less room around 1.75 mm filament. Match what your printer's maker specifies when it names a tube.

Heat limits

Capricorn does not recommend printing above 260 °C with its TL tubing.^[4] The specs page gives TL a melting point of "around 300 °C", but that is a deformation estimate, not a working limit. Capricorn says its temperature figures were approximated by heating samples and watching for deformation, and that printer failures may happen at much lower temperatures.^[3]

A PTFE limit in the hot zone is one reason owners look at an all-metal hotend; the all-metal vs PTFE-lined guide covers that choice. For the Neptune 3 series, ELEGOO says a replacement all-metal throat must match the original 27 mm length.^[1]

When to replace

• Prusa MINI and MINI+: replace a deformed or worn tube. Prusa says to clean the tubes with compressed air and warns that a solid wire can damage them inside.^[2]
• ELEGOO Neptune 3 Pro, Plus and Max: for frequently used printers, ELEGOO recommends replacing the hotend PTFE tubing at least once a month.^[1] ELEGOO also does not recommend carbon fiber filament on these hotends, because it quickly wears the PTFE tube and nozzle.
• Other printers: follow your manual. We found no comparable published interval from other makers.

Genuine Capricorn and where not to buy

Capricorn says it does not sell on AliExpress or Alibaba and neither do its authorized resellers, so tubing bought there is almost certainly not genuine.^[5] It also says it began laser-etching batch numbers onto its tubing in 2023. The buying checklist covers how to check a seller before you order.

Picks that fit1 product

Choose XS, 1 m, for 1.75 mm filament, on a Bowden or feed path whose fittings take a 4 mm outside-diameter tube.

More on choosing

Not for a hotend whose maker specifies its own PTFE length, such as the Neptune 3 series. Capricorn names its authorized Amazon sellers on its resellers page: check that 'Sold by' is one of them, or Amazon.com.

• Capricorn XS series low-friction Bowden tubing, 1 m, 1.75 mm

Next

• All-metal vs PTFE-lined hotends
• Printer maintenance schedules from the makers
• Nozzles for carbon fiber and abrasive filament
• Buying printer parts online: what to check