Once you've designed a custom fan grill and exported the free STL, the next decision is what to print it in. For a part that's purely decorative, sitting on the outside of a case where it's seen and not stressed, the choice really comes down to finish quality and how forgiving the material is with fine detail. Not structural load.
PLA: the easier print, and usually the better looking one
PLA is my default recommendation for a fan grill, and for most designs it's also the better looking result. It holds sharp corners and thin lines well, is less prone to warping on small parts, and takes color and finish more predictably than PETG. If your design has fine detail, text, thin lattice work, tight cutouts, PLA will generally reproduce it more cleanly straight off the printer.
The tradeoff: PLA is more brittle and softens at lower temperatures, so it's not the pick for a grill that'll sit somewhere hot: direct sun, near a radiator, inside a poorly ventilated case with hot components right behind it.
When to use it: most builds, most designs, especially anything with fine detail or text. This is also what we print in house when you order a grill through the site instead of printing your own.
PETG: tougher, slightly less crisp
PETG trades a bit of print crispness for toughness. It's more impact and heat resistant than PLA, so it holds up better if the grill takes the occasional knock or sits somewhere warmer. The tradeoff is that PETG is stringier and more prone to slight blobbing on fine detail, so very thin text or tight lattice patterns can come out a little less clean than the same design printed in PLA. It also tends toward a glossier finish, which some builders want and others really don't.
When to use it: builds that run hot, grills that get bumped or handled a lot, or if you just want PETG's glossier look.
Either way, thin features need care
Whichever filament you pick, thin features are the thing to watch. Fine lattice work, small text, and narrow cutouts are the first things to fail on a print: under extrusion, missed layers, or features so thin they don't hold together when you pull them off the plate. Our editor flags overly thin features while you design, and it's worth actually listening to those warnings before you export. It's a lot faster to widen a line in the editor than to reprint the whole thing.
The simple version
Want the cleanest, most detailed result? Print in PLA. Need it to survive heat or rough handling? Print in PETG. Not sure, or don't want to deal with a printer at all? Order it printed in PLA and shipped to your door, $15 for the first grill and $5 for each additional design.
Either way, start in the editor, export a free STL once you're happy with the design, and check the FAQ for fit and printing details before you slice.