Buying STL files: supports, scale and settings to check

A 3D print file is cheap to buy and expensive to get wrong. The price of the file is rarely the cost that hurts; the cost is the evening of printing, the filament and the model that comes off the bed at the wrong size, snapped where a support should have been. Most of that is avoidable if you read the listing for the right things before you pay.

We read the 3D Printing Models shelf on Getly, measured 26 September 2026, to see what listings actually tell a buyer. The shelf holds 105 active listings. One caution before the numbers: a single shop holds 92.4% of that shelf and writes every description from the same template, so the shares below mostly describe one careful seller's habits, not a whole market. They are still useful, because that template happens to answer most of what a buyer should ask, and its one gap is the same gap you will find on many other sites.

First: what you are actually downloading

On this shelf 95.2% of listings deliver a zip archive. Loose STL files are rare (3.8% of listings) and 3MF appears on 1.0%. The archives are small: the median download is about 0.16 MB, and nine in ten are under half a megabyte. That is normal for simple functional prints and would be suspicious for a detailed miniature, whose meshes usually run far larger.

So the first check is simple: the listing should say what is inside the archive. The good ones list each file by name, for example a main body file, a second file for a two-colour inlay, a print note and a licence text. If a listing says only "STL files included", you do not know whether you are getting one part or twelve.

The format matters too. An STL is geometry only: no units, no colours, no print settings. A 3MF can carry units, several parts, colours and slicer settings in one file, which is why a 3MF from a designer who tested the print is often more useful than an STL of the same model. An OBJ is usually a modelling export and may need cleaning before it slices well.

Supports: the question most listings answer

Whether a model needs supports decides how long it prints, how much material you waste and how much cleanup you do afterwards. On this shelf 85.7% of listings say "no supports" outright, which is the clearest possible answer: the designer oriented the model so it prints flat.

What to look for when a listing is less explicit:

• "Supports required" or "pre-supported". Pre-supported files are common for resin miniatures and save you the work of placing supports yourself. None of the listings on this shelf mention pre-supported files, and only 1.9% mention resin at all, so this is a filament shelf.
• Orientation. A phrase such as "print floor-down" or "print on its back" tells you the designer tested one orientation. If you rotate the model, the support answer may change.
• Overhangs in the preview images. If you see large parts hanging in the air with no note about supports, ask the seller before buying.

Scale: the question most listings skip

Here is the gap. Only about a third of listings on this shelf (33.3%) give any size in millimetres or centimetres, and 12.4% give full dimensions in the "width x depth" form. STL files carry no units at all: a model drawn in millimetres opens at the right size in most slicers, but a model exported in inches or in metres can open tiny or enormous, and you will not know which until you import it.

Before you buy, check for:

• The printed size. Height, width and depth in millimetres, or at least the longest side.
• Whether it fits your printer. Compare the longest side with your build plate. A model that needs splitting is a different project from one that prints in one piece.
• Whether scaling breaks it. Functional parts with holes, threads, hinges or snap fits often stop working if you scale them. A listing should say which size the tolerances were tested at.

If none of that is in the listing, a message to the seller costs less than a failed print.

Print settings: a tested starting point

A good listing tells you what the designer printed with, so you start from a known result instead of guessing. On this shelf 86.7% of listings name a layer height, 83.8% give a wall count, 76.2% give an infill percentage and 86.7% name a material, almost always PLA. A typical line reads: floor-down, PLA, 0.2 mm layers, 3 walls, 15% infill, no supports.

Treat these as a starting point, not a guarantee. Printer brands are mentioned on only 1.9% of listings, and your own printer, nozzle and filament may need small changes. What matters is that someone printed the model once with settings you can repeat.

Price and licence

Prices on this shelf are tightly grouped: the median paid listing costs $4.00, the 10th percentile is $4.00 and the 90th percentile is $4.99. That is the price of a simple functional or decorative print, not of a detailed kit.

Read the licence before you print anything to sell. On this shelf 83.8% of descriptions say "personal use", which means printing for yourself or as a gift, not selling the prints. Only 6.7% of listings have the licence field set on the listing itself; where it is set, it is shown next to the buy button, so check there and in the description.

A two-minute checklist before you pay

1. Does the listing name every file in the archive, and is the format STL, 3MF or OBJ?
2. Does it say whether supports are needed, and in which orientation it was tested?
3. Does it give the printed size in millimetres, and does that fit your build plate?
4. Does it name a layer height, walls, infill and material you can start from?
5. Does the licence allow what you plan to do with the prints?

Browse the 3D Printing Models shelf with this list in hand. If you design printable models yourself, the same five questions are what your description should answer; our guide to selling 3D print files covers the listing side.