Red filament, ranked by £/kg — page 3
Every red filament we track on Amazon UK, ranked by £/kg. Multipacks and dual-colour spools are left out: they belong to no single colour.
136 listings tracked, 35 on offer right now.
Filament by brand
Guides
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Silk filament: how to get the shiny finish
Silk PLA gives prints a metallic sheen, and dual or triple colour silk shifts colour as it turns. What it is, how to print it, and where it falls short.
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Bed adhesion: what actually works
Glue sticks, hairspray, rafts, brims and expensive surfaces — an honest ranking of what fixes prints coming loose, starting with the free fix that solves most cases.
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Do you need a filament dryer?
Wet filament is real and ruins prints, but a dedicated dryer is not the only answer. How to tell if moisture is your problem, and what to do about it.
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Filament storage: dry boxes, vacuum bags and desiccant
Keeping filament dry is cheaper than drying it out. What actually works, what desiccant to use, and why the little sachet in the bag is already spent.
Best-selling Filament by year — which actually sold best, going back several years, ranked by sales position rather than opinion.
What the per-kilo number actually tells you
Filament is sold by the spool, advertised by the discount, and used by the gram. Those three facts are why a spool at “40% off” can be poor value and an unremarkable listing can be the cheapest thing on the page. The only number that compares two listings honestly is what a kilogram costs you, so that is what this page ranks on.
A few things follow from that. Multi-spool bundles are counted at their total weight, so a 4 × 1 kg pack competes directly with a single spool rather than looking four times more expensive. Where a listing does not state a weight we can trust, we leave the per-kilo figure blank instead of guessing — a wrong ranking is worse than a missing one.
Watch for the spool itself. A “1 kg” spool means a kilogram of plastic; the reel is extra and does not count. Refill spools (no reel) are usually a little cheaper and need a holder you already own. And a 750 g spool priced like a 1 kg one is a third more expensive per kilo than it looks — this is the single most common way filament pricing misleads people.
What actually drives the price
Mainstream PLA and PETG from the big value brands sits in a fairly narrow band, and the cheapest listing on any given day is usually just whoever is running a promotion. Paying more buys you, roughly in order of how much it matters:
- Tolerance and consistency. A tighter diameter tolerance (±0.02 mm rather than ±0.05 mm) and properly wound spools mean fewer failed prints. This is the difference you actually notice.
- Additives. Silk, matte, carbon-fibre and glow filaments cost more because the pigment or filler costs more. Carbon fibre also eats brass nozzles.
- Brand. Beyond the two points above, a lot of the premium is brand. Bambu Lab filament is good and priced accordingly; it is not several times better than a solid mid-market spool.
What does not justify a premium: colour, packaging, or a vacuum bag you will throw away. Buy the cheapest spool from a brand that winds its filament properly.
Diameter, and the one mistake worth avoiding
Almost every current printer takes 1.75 mm. A small number of older and industrial machines take 2.85 mm (often labelled 3 mm). They are not interchangeable and the wrong one will not feed. Check before you order, particularly on a bundle — a four-spool pack in the wrong diameter is an expensive mistake, and the listing title is not always clear about it.
How much should you buy at once?
Bundles are usually the better per-kilo price, and filament does not go off if it is kept dry. But PLA and especially PETG, TPU and nylon absorb moisture from the air, and wet filament prints badly — stringing, popping, rough surfaces, weak parts. If you print occasionally, buying four spools to save a pound a kilo is a false economy unless you store them properly. See our guides on filament storage and whether you need a dryer.