There is a spool on the shelf behind me that I have been calling "the grey one" for about fourteen months. It is grey. That is the entire body of knowledge I have about it. Is it PLA? PETG? Something a past version of me bought on sale at 1am with big plans? Nobody knows. Every time I load it I am running a small science experiment, and the hypothesis is always "please don't."
The fix for this has existed the whole time. It is a label. I just didn't want to hand-write eighty of them.
The actual spec sheet part
It is the Marklife P15, a thermal label printer roughly the size of a deck of cards with delusions of grandeur. It pairs to your phone over Bluetooth, you type what you want in the app, and it prints. No ink, no toner, no cartridge to run dry at the worst possible moment. Thermal paper does the whole job by getting warm in the right places, which is the kind of engineering I respect.
It runs about 20 pages per minute, charges over USB, has one button on top, and comes in green, white or black depending on how strongly you feel about that. Most of the listing options ship with a roll or three in the box, and there's a labels-only option if you already own the printer and just want refills.
Why it is actually useful here
Filament spools, obviously. Material, brand, colour, nozzle temp, bed temp, the date you opened it. Slap it on the side and never guess again. That one label ends more failed first layers than most upgrades you'll spend real money on.
Then it keeps going. Label the drawer bins so M3x8 and M3x12 stop living together in sin. Label both ends of every USB-C cable so you know which one is the sad 480Mbps charging cable and which one actually carries data. Label your print profiles taped to each printer. Label the resin bottles. Label the power bricks, because "which laptop does this belong to" is a question that has cost me entire afternoons.
Outside the print room it does spice jars, cable runs behind the desk, storage tote inventories, and the leftovers in the fridge, though I will not be held responsible for what you find in there.
One honest caveat: this is thermal printing, which means the labels fade with heat and sunlight over a long enough timeline. On a spool in a garage that's a non-issue for years. On something bolted to a sunny window, less so. Also, the label rolls are a consumable, so budget for those the same way you budget for filament.
It's sitting at 4.9 stars across 662 reviews with 4,000+ sold, and the reviews mostly say the same two things: it's tiny, and the label paper is cheap. Both true, both the entire point. Check it out here, and may your grey spool finally introduce itself.