A Small Key-Box Upgrade With a Clear Commercial License (2026)

The pick

Small organizers are easy to print and hard to differentiate. This one has a sharper hook: it upgrades a key lock box that property managers, realtors, landlords, short-term-rental hosts, and contractors already use.

Internal Organizer Insert Compatible with Master Lock Key Lock Box is a three-variant STL set by hämppis on Printables. The model was published on July 17, 2026, and the newest revision adds a slotted version alongside the low and high inserts. At the time of checking, the listing showed 2 likes, 2 downloads, 19 views, and no makes, so treat it as a fresh opportunity rather than a proven bestseller. 1

Orange 3D-printed organizer insert fitted inside an open wall-mounted key lock box, with keys visible in the compartment — The slotted insert shown installed inside a compatible key lock box. 1

Why it is sellable

The insert solves a specific annoyance: keys sit loose inside the box instead of staying upright and contained. That makes the product easier to explain in a listing than a generic tray or catch-all bin.

A solo seller has two sensible offers:

Replacement insert: sell one chosen height to buyers who already own a compatible lock box.
Three-version set: bundle the slotted 25 mm, low 25 mm, and high 35 mm versions so the buyer can test fit and keep a spare.

The likely buyer is not shopping for a decorative print. They are trying to make a key handoff setup less messy: a realtor managing showings, a landlord maintaining several properties, an Airbnb host, or a contractor carrying labeled access keys. That is a narrower audience than a general organizer, but the compatibility story gives the listing a useful search phrase and a clear reason to buy.

A reasonable first pricing hypothesis is $8–12 for one insert or $14–18 for the three-version set. Those are suggested test prices, not observed market averages; the value is in the fit and the compatibility story, not in the grams of plastic.

License check before listing

The model is published under Creative Commons Attribution-ShareAlike 4.0 International (CC BY-SA 4.0). The listing explicitly allows commercial use. Give credit to hämppis, and if you modify the STL, distribute the modified design under the same license. 1

Use the original author's name in the product description and keep a copy of the license note with your listing records. The author also states that this is an independent accessory, not affiliated with, endorsed by, or sponsored by Master Lock. Do not use the Master Lock logo or imply brand sponsorship. Check the internal dimensions of the exact lock box before shipping; the author warns that dimensions can vary between models. 1

Files and direct STL links

The official file list contains three STL variants. The slotted version is 25 mm high; the low version is also 25 mm high; the high version is 35 mm high. 2

If a direct file URL has expired, use the model page and download the same filename from the official file list.

Print setup

The author's documented starting point is 20% infill, PETG or a stronger material such as PC or ABS, default STL orientation, and supports recommended. The photographed examples were printed in PETG. 1

Setting	Starting point	Notes
Layer height	0.20 mm	A practical FDM baseline for a functional insert; confirm fit in your slicer.
Nozzle	0.4 mm	Standard nozzle is sufficient for this small part.
Infill	20%	Matches the author's recommendation.
Supports	Recommended	Keep the default orientation, then inspect the screw-hole and underside areas.
Material	PETG	The author's shown prints use PETG; PC or ABS are stronger options if your setup supports them.
Bed adhesion	Clean PEI or a normal PETG setup	No special adhesion method is specified. Add a small brim only if your machine routinely lifts short parts.

Time, material, and difficulty

Plan on roughly 25–40 minutes per insert on a typical 0.4 mm FDM setup at 0.20 mm layers, with supports enabled. That is a planning estimate, not a time published by the designer; let your slicer set the final number. The downloaded STLs contain about 4.4–6.4 cm³ of solid geometry, or roughly 6–8 g of PETG before supports and purge waste. A three-variant sample set should fit comfortably into a small-batch test run.

Difficulty is easy to intermediate. The print itself is small, but fit validation matters more than surface finish. Print one low or slotted sample first, test it in the exact lock box you plan to support, then choose the height and color you will sell.

Filament and listing ideas

Orange PETG: high visibility and easy to spot when a key box is opened.
Black PETG: a discreet replacement look for buyers who want the insert to disappear into the box.
Blue, green, or yellow PETG: useful for color-coding different properties or access groups.

Photograph the insert installed, not just lying on the build plate. Show a key sitting upright, include a ruler or calipers for the 62 × 21 mm footprint, and name the supported lock-box family without claiming brand affiliation. The author lists the insert at 62 × 21 mm, with 25 mm and 35 mm height options and a 5 mm screw-hole diameter; verify your buyer's exact box before shipping. 1

Verdict

Worth a small test batch. The design is not visually flashy, and its early download numbers are modest. Its strength is the combination of a precise fit problem, low material use, three easy-to-explain variants, and a license that explicitly permits commercial use. Sell it as a compatibility-first replacement or organizer insert, and make the fit check impossible to miss.

A Small Key-Box Upgrade With a Clear Commercial License