PTFE feed tubes: compatible diameters, lengths and fittings explained

Guide tube vs. hotend liner: two parts, two jobs

Polytetrafluoroethylene, or PTFE, is a synthetic material best known under the Teflon trade name. According to the Prusa Knowledge Base, its low friction coefficient is why tubes made from it guide filament in every Original Prusa i3 printer. The catch is that one word covers two very different parts that live in different places and face different demands.

The first is the hotend tube. It is part of the hotend assembly inside the extruder. Prusa's documentation notes that this tube is common to all the printers the article covers, single- or multi-material. The second is the tube that guides filament from the spool or the multi-material unit to the extruder. Prusa says this one matters mostly on multi-material printers, such as those running an MMU2.

That distinction changes how you shop. A guide tube usually pulls out by hand, while the hotend tube calls for partial disassembly of the printer. If you are hunting for the right part for a Prusa printer, start by figuring out which of the two you actually need.

Inner and outer diameter: what actually has to match

The outer diameter decides whether the tube seats in the fitting or in the pocket of the extruder. The inner diameter decides how freely filament moves. The Prusa Knowledge Base is blunt about it: not all tubes are the same, so confirm the correct dimensions before you order or cut a new one.

Prusa notes that multi-material systems often need narrower and more precise tubes than a single-material printer. Compare the tubes specified for each position instead of choosing by brand or nominal diameter alone. Before planning a multicolor setup, identify the printer and unit generations, then locate the dimensions and end shapes in the relevant documentation.

Prusa points to dimensioned PTFE illustrations in its documentation. If you buy a tube from another brand, compare its internal dimensions against those drawings instead of trusting the product name. This page stays qualitative on exact figures on purpose: use the manufacturer's trimming guide for the numbers that apply to your specific model.

Tube length depends on your printer generation

You might assume one MK3 hotend tube fits the whole MK3 family. It does not. Prusa's MK3 Series Hotend Guide explains that PTFE tube length differs by exact model: MK3, MK3S, MK3S+ or MK3.5. Since mid-2025, the replacement hotend ships as a universal package. It includes a hotend with a pre-installed tube compatible with the MK3S+ and MK3.5/S, plus separate tubes for the older MK3S and MK3.

Prusa's rule is straightforward. On an MK3S+, MK3.5 or MK3.5S, the pre-installed tube works as is. On an MK3S, swap in the longer tube from the package. On an original MK3, use the longest tube of all. A wrong length is not obvious by eye, which is why you should check the part before fitting it.

The same logic applies to tubes you cut yourself. Prusa points to a dedicated trimming guide for tube specifications and cutting instructions. The shape of the end matters as much as the length: the MK3 hotend guide asks you to insert the tube tapered end first, and the trimming guide defines the geometry expected for your model. A badly cut or badly seated tube is one possible cause of a clogged nozzle, not the only one.

Push fittings: how the tube locks in and how to swap it

For PTFE tube removal on the documented MK3-series hotends, Prusa asks you to press and hold the black collet while pulling out the tube. Identify that fitting in your model's instructions and follow the steps for accessing the assembly first. The tube-removal step does not replace the extruder disassembly instructions.

The MK3 hotend guide then describes reassembly: insert the new tube tapered end first and push it all the way in. While maintaining pressure on the tube, gently lift the collet to lock it. Follow that order and the tube reference specified for the printer; the procedure alone does not make another length or end shape compatible.

The tapered end is not a detail. The MK3 hotend guide asks you to insert it first and push the tube all the way in. A tube inserted backwards or not pushed home will not sit where it should. If extrusion stops mid-print, a tube that is not fully seated is one of several things to check, as covered in the guide on heat creep and stalled extrusion.

Festo or E3D: which tube brand to buy

Prusa's documentation is explicit about its preference. Prusa Research recommends buying tubes manufactured by the company Festo, which in Prusa's words provides the highest quality and precision. That recommendation is written for the Original Prusa i3 printers the article covers; it is not a brand ranking for every printer.

Prusa also accepts E3D tubes, with one condition: always check their internal dimensions and compare them to the PTFE illustrations in the documentation. A well-made tube with the wrong bore is still the wrong tube for your machine. The habit to build is measuring or reading the spec sheet, never assuming a reputable brand is automatically compatible.

Brand is not everything. If you buy a tube from a local supplier, Prusa says to trim it yourself following its trimming guide. Other common brands, such as Capricorn, are not mentioned in the documentation cited here: check their dimensions the same way. To plan consumables like this without blowing your budget, the startup budget tool helps you prioritize.

When to replace a tube and where to get spares

Prusa's documented replacement example combines a jam with a damaged tube. For your printer, identify the affected part and follow the removal and inspection procedure for the exact model. Accessing the hotend tube can require partial disassembly, unlike a guide tube that is generally simpler to remove. Use that service step to confirm the part reference and prepare the replacement before reassembling.

For spares, the Prusa Knowledge Base lists three options. The first is your original shipping box: Prusa includes spare PTFE tubes with some products, notably the MMU2. The second is the manufacturer's online store, which requires logging in to your account. The third is a local PTFE tube supplier, in which case you trim the tube to length yourself using Prusa's trimming guide.

Keeping one or two spare tubes in a drawer saves you from a printer sitting idle. It is one of those small consumables worth a spot on your list of essential accessories, much like a backup nozzle. Just double-check, every time you restock, that the part matches the exact generation of your printer.

Sources and limits

• PTFE tubes in Original Prusa i3 printers | Prusa Knowledge Base Prusa Prusa Prusa
• MK3 Series Hotend Guide | Prusa Knowledge Base Prusa Prusa Prusa

We organize manufacturer and community documentation; we have not measured these products ourselves. The manual for your exact model takes precedence over general guidance.