Filament Spool Terminology Glossary
Updated September 26, 2026
The 3D printing community and manufacturers don't use consistent names for the same hardware. Here's what each term actually means, and which other terms it's commonly confused with.
Reusable spool
A spool designed to be kept and refilled repeatedly, rather than thrown away or recycled after one roll of filament. This is the general, brand-neutral term SpoolNook uses throughout the site. Bambu Lab, SUNLU, and eSUN all sell their own reusable spool hardware.
Master spool
An older, community-originated term for the same basic idea - a reusable hub that refills mount onto - predating most manufacturers' own branded reusable spool products. Widely used in maker communities and on file-sharing sites (Printables, MakerWorld) for adapters and clip designs, largely interchangeable with "reusable spool" in casual use.
Filament refill / refill spool / spool-free filament
All three describe filament sold without its own reusable hub, meant to mount onto a spool you already own. "Spool-free" and "refill" are used interchangeably by most brands; "refill spool" is a looser, sometimes ambiguous term that occasionally gets used to mean the reusable spool itself instead - check context. See filament refill vs. spool for the full distinction.
AMS (Automatic Material System)
Bambu Lab's brand name for its automated multi-material feeder, which holds multiple spools and switches between them mid-print. Often used loosely (including by other brands' users) as a generic term for "automated multi-spool feeder," similar to how "AMS-compatible" gets used to describe spool dimensions even for non-Bambu printers.
MMU (Multi-Material Unit)
Prusa's term for its own multi-material system, conceptually similar to Bambu's AMS but a different mechanism (it splices filament rather than swapping spools via automated feed paths in the same way). Not spool-size-compatible with AMS just because both are "multi-material" systems - check your exact feeder model in the checker.
RFID tag / NFC tag / OpenPrintTag
RFID and NFC are both short-range wireless identification technologies; "RFID tag" is the more general term, while "NFC tag" specifically implies the NFC standard (which Prusament's OpenPrintTag uses). OpenPrintTag is Prusa's specific, openly-published tag format - not a generic term. See RFID and NFC filament tags explained.
Spool hub / spool core
The hub is the reusable spool's central post that a refill's core slides onto. The core is the refill's own central tube (cardboard or plastic) that the filament is wound around. These two parts need to match in diameter for a refill to seat - see how to measure a refill's inner diameter.
Generation (Gen 1, Gen 2, Gen 3...)
A manufacturer's version number for its own spool design over time. Not standardized across brands - SUNLU's "Gen 3" and a hypothetical competitor's "Gen 3" have no relationship to each other. Always check generation against the specific brand you're identifying - see how to identify your reusable spool.
