Will a 2.85 mm spool fit your printer? Check the spec line first

A 2.85 mm spool only works in a printer whose tool head or hotend is built for 2.85 mm. This page shows the spec line that settles it, what seven printer makers list for 19 machines, and how to check a machine with a swapped hotend or tool head.

The short answer

Only if the part of your printer that grips and melts the filament is built for 2.85 mm. The two sizes don't mix. Tubing made for 1.75 mm filament has a bore of about 2 mm, and hotend parts such as E3D's V6 heatsink come in a separate 1.75 mm version, so a 2.85 mm strand can't be fed into a 1.75 mm machine. Going the other way takes different hardware too. A low price doesn't change either fact.

Open your printer maker's specifications page and find the line labeled "Filament diameter". If it says 1.75 mm, skip the 2.85 mm spool and look for the same material in 1.75 mm. If it says 2.85 mm, the size is right, and the other limits are covered in the five limits that decide whether your printer can run a filament. If the line says "Optional" or "Tool Head Dependent", or your hotend has been swapped, the part fitted to your machine decides it. That check is further down.

What printer makers list

Why the brand name isn't enough

One maker can use both sizes. UltiMaker lists 2.85 mm for its S series and 1.75 mm for its Method series. It also groups its own materials by printer series, and its PLA for S series is listed at 2.85 mm.

LulzBot goes further: the same printer can take either size, depending on the tool head. Its Meteor 175 (1.75mm) and Meteor 285 (2.85mm) pages list the same compatible printers, including the Mini 3, SideKick 747, TAZ Workhorse+ and TAZ 8. For its Meteor, Twin Nebula and M175 heads, the number in the name matches the size LulzBot gives: Meteor 175, Twin Nebula 175 and M175 v2 are 1.75mm, while Meteor 285 and Twin Nebula 285 are 2.85mm. Some LulzBot heads, such as the SE, HS and SL, have no size in the name, so open that head's own page.

LulzBot's own TAZ Pro S page shows why the fitted part matters more than the model name. Its spec table says "2.85mm (Standard), 1.75mm (Optional)". The same page names the M175 v2 as the standard tool head and describes a 1.75mm tool head. Go by the tool head that is actually fitted to your machine.

Stand-alone hotends work the same way. E3D's V6 support page lists "Filament diameter: 1.75mm or 2.85mm (depending on variant)" and gives a separate dimension drawing for each. A printer built or upgraded around a V6 could have either. A V6 mention on a spec sheet doesn't settle it, either: Prusa calls the MK4S extruder "E3D V6 compatible (with adapter)" and lists 1.75 mm filament.

What happens if you buy the wrong size

A 2.85 mm spool on a 1.75 mm printer won't feed. Capricorn, which makes PTFE tubing for 1.75 mm filament, lists bores of 1.90 ± 0.05 mm and 2.05 ± 0.05 mm, and gives 2.0 to 2.1 mm as typical for competing white tubing. A 2.85 mm strand is wider than every one of those. Against the largest, 2.1 mm, it works out to 0.75 mm too wide. No slicer or firmware setting changes the size of that bore. This isn't a print-quality problem you can tune away. The filament won't go in.

Going the other way also takes new parts. LulzBot describes its M175 v2 tool head as a way to "add 1.75 mm filament capability" to machines such as the Mini 2, TAZ Workhorse and TAZ Pro. On a V6, the parts the filament runs through are made per size: E3D lists a "Universal V6 1.75mm HeatSink with Coupling", and its V6 HeatBreak page describes 1.75 mm and larger variants. Changing sizes is a parts job, not a setting, and it's a separate project from buying one spool.

Listings sometimes call the larger size 3 mm. E3D does both on its own pages. The V6 page says "1.75mm or 2.85mm" in its summary and "Filament size: 1.75mm / 3.00mm" under Options. The V6 HeatBreak page says "1.75mm and 3mm variants" in one paragraph and "1.75 mm and 2.85 mm variants" in another. For a 1.75 mm printer the difference doesn't matter, because both are far too thick.

For a 2.85 mm printer, it depends on the spool and the machine. None of the sources on this page says whether a spool sold as 3.00 mm runs in a printer listed at 2.85 mm. Before you buy, check two things: the diameter and tolerance the filament maker states on its product page, and the materials your printer maker lists for your machine. UltiMaker, for example, lists its PLA for S series at 2.85 mm. If the spool's figure doesn't match your printer's spec line, ask the printer maker before you order.

How to check your own machine

1. Find the spec line. Bambu Lab, Prusa, Creality, Elegoo and Raise3D label it "Filament diameter"; Bambu Lab puts it in the ToolHead section. UltiMaker says "Compatible filament diameter". LulzBot says "Filament Diameter Compatibility".
2. If the line says "Optional" or "Tool Head Dependent", identify the tool head fitted to your machine, then open that tool head's own page. LulzBot's Meteor 175 and Meteor 285 pages, for example, list the filament diameter in their specifications.
3. If the hotend has been replaced, find out which variant went in, for example from the order or parts list for the upgrade. E3D makes the V6 in both sizes. When you order spares, match the filament size for the parts the filament runs through, such as the heat break, heatsink and tubing. Check that a heater cartridge suits your power supply, as E3D's page advises. If there's no record of the variant, the next step settles it.
4. Measure filament your printer has already fed without trouble. Put calipers across the strand. The two sizes are 1.10 mm apart, which is simply 2.85 minus 1.75, so one reading settles which size you have.
5. Check any feeder in the path. A multi-spool unit has its own limits; Creality lists 1.75±0.05 mm for its CFS. For spool size in a Bambu Lab AMS, see whether a spool will fit your AMS, and for materials it can't handle, filaments the AMS cannot feed.

Once the size matches

Pick the material by what the part has to survive, using choosing filament by heat, stiffness, toughness and moisture. If the spool needs drying first, see whether your dryer reaches the temperature a spool needs.

Check it on your own equipment

These take you to the manufacturers and standards bodies the page draws on, so you can look up your exact model.

• Manufacturer specification
  Check your printer's Filament Diameter line (Bambu Lab A1 shown) (opens in a new tab)Bambu Lab's A1 technical specifications, with "Filament Diameter: 1.75 mm" in the ToolHead section and the included 0.4 mm nozzle on its own line. The A1 mini and H2D spec pages carry the same 1.75 mm row. For another brand, open your model's specifications page and look for the same line. — bambulab.com
• Manufacturer specification
  UltiMaker S5 specifications (opens in a new tab)The row "Compatible filament diameter" reading 2.85 mm, with UltiMaker's note that this is the diameter that achieves optimal results on its S series printers. — ultimaker.com
• Manufacturer specification
  LulzBot Meteor 285 tool head specifications (opens in a new tab)Filament Diameter 2.85mm, a link to the 1.75mm version, and the head's Compatible 3D Printers list. — buy.lulzbot.com
• Official support page
  See E3D's two V6 variants and their dimension drawings (opens in a new tab)The Summary line "Filament diameter: 1.75mm or 2.85mm (depending on variant)", dimension drawings headed 1.75mm and 2.85mm, the Options list for filament size, nozzle size and voltage, and E3D's advice to check the heater cartridge against your power supply. — e3d-online.com