Use a validated PLA Pro for most cool, indoor, static spacers and shims. Choose PETG when moisture, handling abuse, or a warmer environment matters more than maximum rigidity. Choose nylon only when the part also has a real wear, repeated-removal, or low-friction job. For sustained outdoor sun, ASA deserves a separate check.
The material name is only the first gate. Stack-height accuracy, long-term clamp load, temperature, fastener geometry, surface flatness, moisture conditioning, and the consequence of failure decide whether a printed spacer is acceptable. A tougher spool cannot rescue a bad load path or an unmeasured shim.
Disclosure: This page contains affiliate links. GoodPrints may earn a commission at no extra cost to you. This is a manufacturer-documented buyer analysis, not a hands-on durability test. Prusa's PLA, PETG, polyamide, and ASA guidance was checked August 2, 2026.
Quick material decision
| Spacer or shim duty | Start with | Why | Main stop condition |
|---|---|---|---|
| Cool indoor alignment, stack-height correction, or fixture setup | Validated PLA Pro | A rigid, easy-to-print first lane when the exact formulation and installed load are suitable. | Heat, sustained compression, impact, or safety-critical use exceeds the proof. |
| Garage, damp utility space, assembly handling, or moderate warmth | PETG | Useful toughness, low warping, and temperature resistance with less workflow burden than nylon. | Compliance or creep moves stack height outside tolerance. |
| Wear spacer, rub strip, repeated disassembly, or low-speed sliding contact | Qualified nylon | Toughness and low-friction behavior can fit a real wear role. | Moisture, dimensional movement, printer limits, or grade uncertainty defeats the fit requirement. |
| Outdoor, sun-exposed static spacing | ASA | UV and temperature resistance make it a stronger outdoor candidate than choosing by toughness alone. | Enclosure, ventilation, shrinkage, or exact-grade limits are not controlled. |
| Bearing preload, vehicle safety system, pressure boundary, structural joint, or inaccessible critical assembly | Specified commercial part | Traceable material, tolerances, and validation matter more than desktop print convenience. | Do not approve from this guide or one test print. |
What the published material guidance supports
Prusa describes PLA as easy to print and suited to detailed models while warning about brittleness and low temperature resistance. “PLA Pro” or “PLA+” is not one universal formulation, so the label does not prove a common heat, creep, or impact rating. Check the exact spool's technical data and qualify the printed part.
Prusa's PETG guidance identifies low warping, useful temperature resistance, and mechanical-part use. That supports PETG as the practical step-up for rougher or warmer spacing jobs, but it does not guarantee that a thin shim will preserve thickness under every sustained clamp load.
Prusa describes polyamide (nylon) as tough, low-friction, and temperature resistant, while emphasizing moisture absorption and a harder printing workflow. Nylon belongs here when the spacer is partly a wear component—not because “engineering material” automatically means greater dimensional trust.
Prusa's ASA guidance supports its outdoor lane through UV and temperature resistance, with enclosure and ventilation considerations. Use the PETG-versus-ASA outdoor decision when exposure, rather than indoor stack height, is the dominant problem.
Buying shortcut for cool, static indoor spacing: Matte Black AF PLA+ is a live GoodPrints candidate for non-wearing spacers, setup blocks, cosmetic stand-offs, and shims used in temperature-controlled rooms where stiffness and crisp dimensions matter more than heat or fatigue margin.
- Good fit: low-consequence parts that stay dry, cool, static, and lightly loaded after the complete assembly passes measurement and clamp checks.
- Skip this shortcut: bearing surfaces, sliding wear, engine bays, outdoor exposure, hot enclosures, high clamp loads, sustained bending, impact, vibration-critical joints, or safety-related hardware.
- Naming boundary: PLA+ and PLA Pro are not standardized material classes. Treat this spool as a candidate for the guide's rigid PLA-family branch, not as a guaranteed substitute for every PLA Pro formulation.
Shop Matte Black AF PLA+ on GoodPrints
GoodPrints sells this live Shopify Collective product directly. Inventory can change; the product page is the current source for availability.
Start with PLA Pro for cool static spacing
A validated PLA Pro is the clean first candidate for fixture spacers, panel stand-offs, setup blocks, non-hot electronics spacing, furniture alignment, and fit-correction shims that mostly stay still. The point is not that every PLA Pro is strongest. The point is that a rigid, predictable print can make a static dimension easier to inspect.
Use the PLA Pro decision guide to separate this tougher-PLA lane from standard PLA marketing. Reject it when the installed part sees a warm enclosure, parked-vehicle heat, sustained high compression, repeated impact, solvent exposure, or consequences that the exact product data and representative proof do not cover.
Choose PETG when the environment gets rougher
PETG is the honest middle lane for utility spacers that may be handled, splashed, knocked, or installed in a warmer garage or enclosure. It is often easier to own than nylon and more appropriate than PLA for a part whose environment is the real risk.
Do not translate “tougher” into “more accurate.” A PETG shim can still move under sustained load, print with edge buildup, or measure differently after cooling. If PETG's broader utility-part role is the real question, use the functional PETG guide before buying a special spool for one shim.
Choose nylon for wear duty, not status
Nylon starts to earn its workflow when a spacer also rubs, slides, gets removed repeatedly, or acts as a sacrificial machine-side separator. That overlaps the bushings and wear-surfaces guide. If there is no wear or repeated motion, nylon may add moisture and dimensional-control work without solving the real problem.
Use the nylon functional-parts buyer guide to decide whether the printer, dryer, nozzle, enclosure, and exact grade fit the job. Filled nylon is a separate decision: fibers can change stiffness, abrasion, surface finish, nozzle requirements, and small-feature behavior. Do not inherit the verdict for unfilled nylon.
Audit load, temperature, and geometry before slicing
- Name the controlled dimension. Record the required finished thickness, outside dimensions, hole position, flatness, and allowable variation instead of calling the part “about 2 mm.”
- Separate spacing from bearing. Decide whether the plastic merely locates parts or carries fastener preload, a bearing, a moving shaft, or a structural load.
- Record the environment. Measure the likely temperature range and note sun, moisture, oils, cleaners, vibration, and impact. Use the exact filament maker's data.
- Check the fastener interface. Small contact areas and over-tightened screws can crush or dish a printed spacer. Washers, shoulders, metal sleeves, or a commercial spacer may be the real fix.
- Check the failure consequence. If a thickness change can affect steering, braking, guarding, electrical isolation, pressure containment, fire safety, or an expensive assembly, move to an appropriately specified part and qualified process.
Print and measure the dimension that matters
Print orientation changes which surfaces define thickness and how the load crosses layer interfaces. First-layer expansion, top-surface buildup, seam placement, and support contact can all distort a small shim. A CAD thickness is not the accepted thickness.
Print several samples in the intended orientation with the intended machine, nozzle, profile, plate, and conditioned material. Let them cool, remove edge artifacts without rounding the working face, and measure multiple points. If the spacer clamps between hard surfaces, inspect parallelism and contact area—not just one caliper reading.
Very thin adjustments may be better served by commercial shim stock. A printed layer strategy can be useful, but the slicer's nominal layer height does not prove the finished part's thickness, flatness, or long-term behavior.
Run a representative compression and environment proof
- Print at least three samples so one convenient result does not become the specification.
- Measure and label each sample after cooling and after any required material conditioning.
- Install one with the real mating surfaces, washer or sleeve arrangement, and documented fastener procedure.
- Apply the representative load and environment. Include heat, moisture, vibration, or outdoor exposure when those are part of service.
- Re-measure after an early interval and again after a longer representative dwell. Record thickness loss, dish, cracks, loosened preload, and surface imprint.
- Unload and inspect recovery. Define acceptance and replacement limits before producing a batch.
Change one variable at a time. If the first sample dishes under a screw head, fix the contact geometry before buying nylon. If nylon dimensions wander with moisture, stabilize the material state before changing slicer compensation.
Failure symptoms and the first check
| Symptom | Check first | Likely decision |
|---|---|---|
| Thickness varies across one face | First layer, top surface, edge flare, warping, and measurement method | Fix process before changing polymer. |
| Spacer dishes under the fastener | Washer area, sleeve, torque procedure, infill and wall geometry | Redesign the load path or use metal. |
| Fit changes after warm service | Actual local temperature and sustained compression | Use exact grade data and repeat the heat proof. |
| Wear dust or rubbing appears | Alignment, motion, contact pressure, and whether this is really a bushing | Move to the wear-surface lane. |
| Nylon dimensions are inconsistent | Drying, storage, conditioning, extrusion, and exact grade | Control moisture before tuning compensation. |
Buy one spool only after the service lane is clear: choose Matte Black AF PLA+ for crisp, low-risk, cool indoor spacers and shims. Stay with PETG for warmer or rougher utility service, qualified nylon for recurring wear, ASA for outdoor exposure, and specified commercial hardware when failure consequences are meaningful.
Before repeating the part, print the worst-credible thickness, install it with the final fasteners and clamp load, measure the controlled stack dimension, and repeat the heat, time, vibration, or compression exposure the assembly will actually see. Reject cracking, whitening, creep, crushed layers, loosened hardware, rocking, drift, or loss of alignment.
Check current Matte Black AF PLA+ availability
A passing spacer is a material, geometry, print, hardware, and environment system - not a promise made by the spool label.
Final verdict
Use a validated PLA Pro for cool indoor static spacers, PETG for warmer or rougher utility service, qualified nylon for real wear duty, and ASA for sun-exposed outdoor spacing. Measure the printed part, prove it under the actual clamp load and environment, and stop at a specified commercial spacer or shim when the tolerance or failure consequence exceeds what a desktop workflow can responsibly qualify.
FAQ
Is PLA Pro always better than PETG for shims?
No. PLA Pro can be the more rigid indoor candidate, while PETG can be the better environmental fit. Neither label proves long-term thickness under your load; the exact formulation and proof decide.
Should a printed spacer carry bolt preload?
Only when the design, material data, contact geometry, torque procedure, and representative dwell test support it. A metal sleeve or commercial spacer is often cleaner when preload must stay controlled.
Is nylon best for precision stack height?
Not automatically. Nylon can fit wear and repeated-handling duty, but moisture and grade-specific dimensional behavior may work against a tight static spacing requirement.
What is best for outdoor spacers?
ASA is the stronger first candidate when UV exposure is central. PETG can still fit some outdoor utility jobs, but check the exact grade, temperature, sun, load, and expected life.
How thin can a printed shim be?
There is no universal minimum that guarantees thickness or flatness. Print and measure representative samples; use commercial shim stock when the adjustment is too thin or critical for the process to prove.
Choose the next move
- If material or fit is still unresolved, use the custom-part material guide, then move into the replacement-part intake guide if an existing spacer must be matched.
- If the part is occasional and you do not need to own the process, compare owning a printer with using a print service before building a workflow around one shim or spacer job.
- If the dimensions and quantity are already known, use JC Print Farm while tolerance, material, or sample strategy needs review, or request a quote once the file, quantity, material, and timing are defined.
If this page is turning into a real next-step decision, start here
This spacers-and-shims page works better when it gives readers one fit-check branch, one practical everyday dryer lane, and one heavier nylon-capable recovery step instead of pretending the whole decision ends at material names alone.
If your real remaining risk is that the spacer or shim job only works once the dimensions stop being hopeful guesses: the VINCA IP54 caliper is the cleaner first buy. It fits readers whose next move is better fit-check confidence before changing the material story again. The tighter on-site handoff is the VINCA review.
If PETG or tougher everyday spools keep drifting between sessions and that inconsistency is what makes the material comparison feel messier than it should: the Space Pi Dryer Plus is the calmer support branch. It matches readers whose better result starts with more reliable active-spool recovery. The tighter on-site handoff is the Space Pi Plus review.
If the only reason nylon stays in the conversation is that you are ready for a more serious moisture-control step instead of hoping storage alone carries it: the EIBOS Polyphemus is the stronger branch. It fits readers whose shim or spacer use case is genuinely pushing into fussier material territory. The tighter on-site handoff is the EIBOS Polyphemus review.
That keeps the monetization compact and high-fit: one better caliper, one practical recovery dryer, and one heavier moisture-control branch for the readers whose shim or spacer lane is getting more demanding.